[AArch64][SVE] Fold vselect into predicated fmul, fsub and fadd

Fold vselect with an unpredicated fmul/fsub/fadd
operand into a predicated fmul/fsub/fadd:

(vselect (p) (op (a) (b)) (a)) => (op -> (p) (a) (b))

Differential Revision: https://reviews.llvm.org/D117689