[CodeGen] Simplify expandRoundInexactToOdd (#134988)
FP_ROUND and FP_EXTEND the input value before FABSing it. This avoids
some bit twiddling to copy the sign bit from the input to the result. It
does introduce one extra FABS, but that is folded into another
instruction for free on AMDGPU, which is the only target currently
affected by this change.
