S/390: Fix ifunc missing runtime reloc

S/390: Fix ifunc missing runtime reloc

This fixes a problem with a missing R_390_64 reloc against .data for a
function pointer to an ifunc function.

No regressions on s390x.

Pushed to mainline.

bfd/ChangeLog:

2017-05-08  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	* elf-s390-common.c: Don't check non_got_ref flag.
	* elf32-s390.c (elf_s390_relocate_section): Likewise.
	* elf64-s390.c (elf_s390_relocate_section): Likewise.