PR22166, SHT_GNU_verneed memory allocation

PR22166, SHT_GNU_verneed memory allocation

The sanity check covers the previous minimim size, plus that the size
is at least enough for sh_info verneed entries.

Also, since we write all verneed fields or exit with an error, there
isn't any need to zero the memory allocated for verneed entries.

	PR 22166
	* elf.c (_bfd_elf_slurp_version_tables): Test sh_info on
	SHT_GNU_verneed section for sanity.  Don't zalloc memory for
	verref.