MC: Introduce R_AARCH64_PATCHINST relocation type.
The R_AARCH64_PATCHINST relocation type is to support deactivation
symbols. For more information, see the RFC:
https://discourse.llvm.org/t/rfc-deactivation-symbols/85556
Part of the AArch64 psABI extension:
https://github.com/ARM-software/abi-aa/issues/340
