[llvm] [AArch64] Mark FMOVvXfY_ns as rematerializable, cheap (PR #169186)

[Tomer Shafir via llvm-commits]

https://github.com/tomershafir requested changes to this pull request.

Pls add a test for all of the variants that verifies they get rematerialized

https://github.com/llvm/llvm-project/pull/169186