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

[Tomer Shafir via llvm-commits]

tomershafir wrote:

Note: In theory, this can regress a workload by reducing the number of ZCMs if there is no register pressure, but seems reasonable until we are able to fill this gap.

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