[DAGCombiner] skip reciprocal divisor optimization for x/sqrt(x)

In general, we probably want to try the multi-use reciprocal

transform before sqrt transforms, but x/sqrt(x) is a special-case

because that will always reduce to plain sqrt(x) or an estimate.

The AArch64 tests show that the transform is limited by TLI

hook to patterns where there are 3 or more uses of the divisor.

So this change can result in an extra division compared to

what we had, but that's the intended behvior based on the

current setting of that hook.