[LoongArch] Added spill/reload/copy support for CFRs

[LoongArch] Added spill/reload/copy support for CFRs

1, spill/reload
When a function call is made immediately after a floating point
comparison, the result of the comparison needs to be spilled before
function call and reloaded after the function returns.

2, copy
Support `GPR` to `CFR` and `CFR` to `GRP` copys. Therefore, the correct
register class can be used in the pattern template, and the hard-coding
of mutual coping of `CFR` and `GRP` is eliminated, reducing redundant
comparison instructions.

Note: Since the `COPY` instruction between CFRs is not provided in
LoongArch, we only use `$fcc0` in the register allocation.

Reviewed By: SixWeining

Differential Revision: https://reviews.llvm.org/D137004