[PowerPC] Fix the unexpected modification caused by D62993 in LowerSELECT_CC for power9

Summary:
The patch D62993 : `[PowerPC] Emit scalar min/max instructions with unsafe fp math`
has modified the functionality when `Subtarget.hasP9Vector() && (!HasNoInfs || !HasNoNaNs)`,
 this modification is not expected.

Reviewed By: nemanjai

Differential Revision: https://reviews.llvm.org/D74701