MIPS/Clang: handleTargetFeatures, add +fp64 if +msa and no other +-fp (#92728)

Commit: d59bc6b5
Clang/MIPS: Add +fp64 if MSA and no explicit -mfp option (#91949)
added +fp64 for `clang`, while not for `clang -cc1`. So

   clang -cc1 -triple=mips -target-feature +msa -S

will emit an asm source file without ".module fp=64".