[AArch64] Add missing system register for v8.9-A/v9.4-A Permission Indirection Extension

This adds support for the missing `PIRE0_EL12` system register, part of
v8.9-A/v9.4-A's Permission Indirection Extension.

Patch by Son Tuan Vu.

Reviewed By: tmatheson

Differential Revision: https://reviews.llvm.org/D141400