[clang] [llvm] [NFC][AArch64][TableGen] Define ZA, ZT0 and FPMR memory defvars (PR #154144)

[Paul Walker via cfe-commits]

paulwalker-arm wrote:

Thanks for splitting the PR Carol.  For the final PR that switches the intrinsics to use target-memory we shouldn't need auto-upgrade specific changes but we will need to upgrade the memory-effects of existing functions when reading old bitcode.  This means you'll need to update the ME version number when writing (BitcodeWriter.cpp) and update the reader (BitcodeReader.cpp) so prior versions broadcast the current inaccessible-memory effects across the target-memory locations that have become live.  This is effectively making target-memory ready for production so you'll also need to update the LangRef.

One caveat here is I think we only want to do the inaccessible-to-target broadcast for AArch64 targets because no other target has decided what they want to use them for yet.

https://github.com/llvm/llvm-project/pull/154144