PowerPC64 dynamic symbol tweaks

PowerPC64 dynamic symbol tweaks

In check_relocs, bfd_link_pic true means ld is producing a shared
library or a position independent executable.  !bfd_link_pic means a
fixed position (ie. static) executable since the relocatable linking
case is excluded.  So it is appropriate to continue using bfd_link_pic
when testing whether non-pcrelative relocations should be dynamic, and
!bfd_link_pic for the special case of ifunc in static executables.
However, -Bsymbolic shouldn't affect PIEs (they are executables so
none of their symbols should be overridden) and PIEs can support copy
relocations, thus bfd_link_executable should be used in those cases
rather than bfd_link_pic.

I've also removed the test of ELIMINATE_COPY_RELOCS in check_relocs.
We can sort out what to do regarding copy relocs later, which allows
the code in check_relocs to be simplified.

	* elf64-ppc.c (ppc64_elf_check_relocs): Use bfd_link_executable
	in choosing between different actions for shared library and
	non-shared library cases.  Delete ELIMINATE_COPY_RELOCS test.
	(dec_dynrel_count): Likewise.  Account for ifunc special case.
	(ppc64_elf_adjust_dynamic_symbol): Copy relocs are for executables,
	not non-pic.
	(allocate_dynrelocs): Comment fixes.  Delete ELIMINATE_COPY_RELOCS
	test.