[X86] When selecting (x << C1) op C2 as (x op (C2>>C1)) << C1, use the operation...

[X86] When selecting (x << C1) op C2 as (x op (C2>>C1)) << C1, use the operation VT for the target constant.

Normally when the nodes we use here(AND32ri8 for example) are selected their
immediates are just converted from ConstantSDNode to TargetConstantSDNode
without changing VT from the original operation VT. So we should still be
emitting them with the operation VT.

Theoretically this could expose more accurate opportunities for CSE.

llvm-svn: 356869