[RISCV] Add support for XCVmac extension in CV32E40P

Implement XCVmac intrinsics for CV32E40P according to the specification.

This is the first commit of a patch-set to upstream the 7 vendor specific extensions of CV32E40P.

The patch-set aims at upstreaming the extensions on MC. The following will be on CodeGen, and the final patch-set will be on builtins if possible. The implemented version is on [0].

Contributors: @CharKeaney, Serkan Muhcu, @jeremybennett, @lewis-revill, @liaolucy, @simoncook, @xmj

Spec: https://github.com/openhwgroup/cv32e40p/blob/62bec66b36182215e18c9cf10f723567e23878e9/docs/source/instruction_set_extensions.rst

[0] https://github.com/openhwgroup/corev-llvm-project

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D152821