[objdump][macho] Check arch before formating reloc name as arm64 addend

Before formating ARM64_RELOC_ADDEND relocation target name as a hex
number, the architecture need to be checked since other architectures
can define a different relocation type with the same integer as
ARM64_RELOC_ADDEND.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D89094