[llvm] [AArch64][GlobalISel] Fix invalid subregister copies for truncating stores (PR #213935)

[David Green via llvm-commits]

https://github.com/davemgreen commented:

Is this codepath only intended to be used for FPR? The anyext load code below is guarded by a FPR RB check, could the same thing be done here? Or do we generate trunc stores for i64->i32?

https://github.com/llvm/llvm-project/pull/213935