Fix Sparc, s390 and AArch64 targets so that they can handle relocs against ifunc...

Fix Sparc, s390 and AArch64 targets so that they can handle relocs against ifunc symbols found in note sections.

  Following on from PR 22929, I have found the same problem exists with
  other ifunc supporting targets too.  Plus see this link for the bug
  being reported against the s390x binutils for Fedora rawhide:

     https://bugzilla.redhat.com/show_bug.cgi?id=1553705

  So I am going to check in the patch below which applies the same
  change that H.J. made for the x86_64 target to the other affected
  targets.  (Specifically: S390, AArch64 and Sparc).  Plus it adds a new
  test to the linker testsuite to make sure that this problem stays
  fixed.

bfd	* elf64-s390.c (elf_s390_relocate_section): Move check for
	relocations against non-allocated sections to before the code that
	handles ifunc relocations.
	* elf32-s390.c (elf_s390_relocate_section): Likewise.
	* elfnn-aarch64.c (elfNN_aarch64_final_link_relocate): Treat
	relocs against IFUNC symbols in non-allocated sections as relocs
	against FUNC symbols.
	* elfxx-sparc.c (_bfd_sparc_elf_relocate_section): Likewise.

ld	* testsuite/ld-ifunc/ifuncmod5.s: New test.  Checks that targets
	that support IFUNC symbols can handle relocations against those
	symbols in NOTE sections.
	* testsuite/ld-ifunc/ifuncmod5.d: New file:  Driver for the new
	test.
	* testsuite/ld-ifunc/ifunc.exp: Run the new test.