[AArch64][SME] Add some SME PSTATE setting/query intrinsics

This patch adds support for:

* Querying the PSTATE.SM state with @llvm.aarch64.sme.get.pstatesm
* Reading/writing the TPIDR2 register with new
@llvm.aarch64.sme.get.tpidr2 and @llvm.aarch64.sme.set.tpidr2
intrinsics.

Tests added here:

  CodeGen/AArch64/sme-get-pstatesm.ll
  CodeGen/AArch64/sme-read-write-tpidr2.ll

Differential Revision: https://reviews.llvm.org/D127957