[PowerPC] Handle FP physical register in inline asm constraint.

Do not defer to the base class when the register constraint is a
physical fpr. The base class will select SPILLTOVSRRC as the register
class and register allocation will fail on subtargets without VSX
registers.

Differential Revision: https://reviews.llvm.org/D91629

GitOrigin-RevId: 4e127bce2d1133ba95a551d69bd0e8fc3b4f9e71
3 files changed