[clang] [Clang][LoongArch] Match GCC behaviour when parsing FPRs in asm clobbers (PR #138391)

[WÁNG Xuěruì via cfe-commits]

https://github.com/xen0n commented:

Thank you for the patch!

Test assertions can be updated as well -- check for two occurrences of the respective `asm` statement.

https://github.com/llvm/llvm-project/pull/138391