PR17488, powerpc64-linux-ld segfault

PR17488, powerpc64-linux-ld segfault

For binary ouput, we don't have an ELF bfd output so can't access
elf_elfheader.  The elf64-ppc.c changes are really just a tidy,
triggered by looking at all places where the abiversion bits are
accessed.

bfd/
	* elf64-ppc.c (ppc64_elf_before_check_relocs): Do .opd processing
	even when output is not ppc64 ELF.  Remove redundant tests on
	type of input bfd.
ld/
	PR 17488
	* emultempl/ppc64elf.em (gld${EMULATION_NAME}_finish): Don't attempt
	to access ELF header e_flags when not ppc64 ELF output.