[llvm] [RISCV] Set the isMoveReg flag for FMV_X_W (PR #109378)

[Yingwei Zheng via llvm-commits]

https://github.com/dtcxzyw commented:

IIRC `isMoveReg` only applies to copies within the same register class or `reg <-> subreg` copies. Have you seen other targets set this flag for `fp <-> int` moves?


https://github.com/llvm/llvm-project/pull/109378