[RISCV] Use hasAllWUsers to recover ANDI.

SimplifyDemandedBits can 0 the upper bits and targetShrinkDemandedConstant
isn't alway able to recover it.

At least part of that may be because targetShrinkDemandedConstant
only runs in the last DAGCombine. Might be worth seeing what happens
if we move it post type legalization.