[llvm] [AArch64][SVE2] Use a PatFrag for URSHR (PR #81304)

[Paul Walker via llvm-commits]

https://github.com/paulwalker-arm approved this pull request.

Thanks for this.

FYI: I've missed the fact these instruction patterns don’t have good MOVPRFX support so there’s still a source of confusion but I’m happy enough now the DAG side of things is clean. I’ll circle back to this once I’ve resolved the problematic part of MOVPFX support within the register allocator.

https://github.com/llvm/llvm-project/pull/81304