bfd: Add support for LoongArch64 EFI (efi-*-loongarch64).

bfd: Add support for LoongArch64 EFI (efi-*-loongarch64).

This adds support for efi-loongarch64 by virtue of adding a new PEI target
pei-loongarch64.  This is not a full target and only exists to support EFI at
this time.

This means that this target does not support relocation processing and is mostly
a container format.  This format has been added to elf based loongarch64 targets
such that efi images can be made natively on Linux.

However this target is not valid for use with gas but only with objcopy.

We should't limit addresses to 32-bits for 64-bit vma, otherwise there will be
"RVA truncated" error when using objcopy on loongarch64.

With these changes the resulting file is recognized as an efi image.

Any magic number is based on the Microsoft PE specification [1].

The test results are as follows:
$ make check-binutils RUNTESTFLAGS='loongarch64.exp'
  PASS: Check if efi app format is recognized

$ objdump -h -f tmpdir/loongarch64copy.o
  tmpdir/loongarch64copy.o:     file format pei-loongarch64
  architecture: Loongarch64, flags 0x00000132:
  EXEC_P, HAS_SYMS, HAS_LOCALS, D_PAGED
  start address 0x0000000000000000

  Sections:
  Idx Name          Size      VMA               LMA               File off  Algn
    0 .text         0000003c  00000000200000b0  00000000200000b0  00000200  2**2
                    CONTENTS, ALLOC, LOAD, READONLY, CODE

[1] https://docs.microsoft.com/en-us/windows/win32/debug/pe-format

bfd:
  * .gitignore (pe-loongarch64igen.c): New.
  * Makefile.am (pei-loongarch64.lo, pe-loongarch64igen.lo, pei-loongarch64.c,
  pe-loongarch64igen.c): Add support.
  * Makefile.in: Likewise.
  * bfd.c (bfd_get_sign_extend_vma): Add pei-loongarch64.
  * coff-loongarch64.c: New file.
  * coffcode.h (coff_set_arch_mach_hook, coff_set_flags,
  coff_write_object_contents) Add loongarch64 (loongarch64_pei_vec) support.
  * config.bfd: Likewise.
  * configure: Likewise.
  * configure.ac: Likewise.
  * libpei.h (GET_OPTHDR_IMAGE_BASE, PUT_OPTHDR_IMAGE_BASE,
  GET_OPTHDR_SIZE_OF_STACK_RESERVE, PUT_OPTHDR_SIZE_OF_STACK_RESERVE,
  GET_OPTHDR_SIZE_OF_STACK_COMMIT, PUT_OPTHDR_SIZE_OF_STACK_COMMIT,
  GET_OPTHDR_SIZE_OF_HEAP_RESERVE, PUT_OPTHDR_SIZE_OF_HEAP_RESERVE,
  GET_OPTHDR_SIZE_OF_HEAP_COMMIT, PUT_OPTHDR_SIZE_OF_HEAP_COMMIT,
  GET_PDATA_ENTRY, _bfd_peLoongArch64_bfd_copy_private_bfd_data_common,
  _bfd_peLoongArch64_bfd_copy_private_section_data,
  _bfd_peLoongArch64_get_symbol_info, _bfd_peLoongArch64_only_swap_filehdr_out,
  _bfd_peLoongArch64_print_private_bfd_data_common,
  _bfd_peLoongArch64i_final_link_postscript,
  _bfd_peLoongArch64i_only_swap_filehdr_out, _bfd_peLoongArch64i_swap_aouthdr_in,
  _bfd_peLoongArch64i_swap_aouthdr_out, _bfd_peLoongArch64i_swap_aux_in,
  _bfd_peLoongArch64i_swap_aux_out, _bfd_peLoongArch64i_swap_lineno_in,
  _bfd_peLoongArch64i_swap_lineno_out, _bfd_peLoongArch64i_swap_scnhdr_out,
  _bfd_peLoongArch64i_swap_sym_in, _bfd_peLoongArch64i_swap_sym_out,
  _bfd_peLoongArch64i_swap_debugdir_in, _bfd_peLoongArch64i_swap_debugdir_out,
  _bfd_peLoongArch64i_write_codeview_record,
  _bfd_peLoongArch64i_slurp_codeview_record,
  _bfd_peLoongArch64_print_ce_compressed_pdata): New.
  * peXXigen.c (_bfd_XXi_swap_aouthdr_in, _bfd_XXi_swap_aouthdr_out,
  _bfd_XXi_swap_scnhdr_out, pe_print_pdata, _bfd_XX_print_private_bfd_data_common,
  _bfd_XX_bfd_copy_private_section_data, _bfd_XXi_final_link_postscript):
  Support COFF_WITH_peLoongArch64,
  * pei-loongarch64.c: New file.
  * peicode.h (coff_swap_scnhdr_in, pe_ILF_build_a_bfd, pe_ILF_object_p):
  Support COFF_WITH_peLoongArch64.
  (jtab): Add dummy entry that traps.
  * targets.c (loongarch64_pei_vec): New.

binutils
  * testsuite/binutils-all/loongarch64/loongarch64.exp: New file.
  * testsuite/binutils-all/loongarch64/pei-loongarch64.d: New test.
  * testsuite/binutils-all/loongarch64/pei-loongarch64.s: New test.

include
  * coff/loongarch64.h: New file.
  * coff/pe.h (IMAGE_FILE_MACHINE_LOONGARCH64): New.

Signed-off-by: Youling Tang <tangyouling@loongson.cn>