[clang] [llvm] [RISCV] Add Qualcomm uC Xqcicsr (CSR) extension (PR #117169)

[Sam Elliott via cfe-commits]

https://github.com/lenary approved this pull request.

I am out of the loop on the discussion in the call today, but I can confirm this is a correct implementation of Xqcicsr, according to the specification.

https://github.com/llvm/llvm-project/pull/117169