[BFD, AArch64] Define elf_backend_fixup_gnu_properties in AArch64
This patch add support for elf_backend_fixup_gnu_properties for GNU
property support for AArch64. The new AArch64 specific definition
_bfd_aarch64_elf_link_fixup_gnu_properties goes through the property
list to find AArch64 type properties and removes the properties that
are marked as "property_remove".