[llvm] [AArch64] Remove redundant fmovs when bitcasting from ext/trunc of bitcast (PR #175983)

[David Green via llvm-commits]

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

I'm not sure how much these will help in practice, but they look OK to me and I was hoping to use something similar for GISel. LGTM

https://github.com/llvm/llvm-project/pull/175983