PowerPC/BFD: Convert `%P: %H:' to `%H:' in error messages

PowerPC/BFD: Convert `%P: %H:' to `%H:' in error messages

Remove an inconsistency in BFD linker error messages across the PowerPC
backends, where in the presence of line information the `%P: %H:' format
sequence makes the first error message produced for any given function
different from subsequent ones.

Taking the `ld/testsuite/ld-powerpc/tocopt7.s' test case source as an
example and the `powerpc-linux' target we have:

$ as -gdwarf2 -o tocopt.o -a64 tocopt.s
$ ld -o tocopt -melf64ppc tocopt.o
ld: tocopt.o: In function `_start':
tocopt.s:35:(.text+0x14): toc optimization is not supported for 0x3fa00000 instruction.
ld: tocopt.s:49:(.text+0x34): toc optimization is not supported for 0x3fa00000 instruction.
$

where the first error message does not have the source file name
prefixed with the linker program executable's name, i.e. `ld:', whereas
the second error message does, as would any subsequent.

This is because with a multiple-line error message such as `%H' produces
`%P' only prints the program executable's name on the first line and not
any later ones.  Also the PowerPC backend is the only part of BFD which
uses `%P' along with one of the clever `%C', `%D', `%G', `%H' format
specifiers.  And last but not least this breaks a GNU Coding Standard's
requirement that error messages from compilers should look like this:

source-file-name:lineno: message

also quoted in `vfinfo' code handling these specifiers.

Convert `%P: %H:' to `%H:' in error messages across the PowerPC backends
then, yielding:

$ as -gdwarf2 -o tocopt.o -a64 tocopt.s
$ ld -o tocopt -melf64ppc tocopt.o
tocopt.o: In function `_start':
tocopt.s:35:(.text+0x14): toc optimization is not supported for 0x3fa00000 instruction.
tocopt.s:49:(.text+0x34): toc optimization is not supported for 0x3fa00000 instruction.
$

instead, making it consistent and matching the GNU Coding Standard's
requirement.

	bfd/
	* elf32-ppc.c (ppc_elf_check_relocs): Use `%H:' rather than
	`%P: %H:' with `info->callbacks->einfo'.
	(ppc_elf_relocate_section): Likewise.
	* elf64-ppc.c (ppc64_elf_check_relocs): Likewise.
	(ppc64_elf_edit_toc): Likewise.
	(ppc64_elf_relocate_section): Likewise.