[Hexagon] Undo shift folding where it could simplify addressing mode

For example, avoid (single shift):
  r0 = and(##536870908,lsr(r0,#3))
  r0 = memw(r1+r0<<#0)

in favor of (two shifts):
  r0 = lsr(r0,#5)
  r0 = memw(r1+r0<<#2)

llvm-svn: 296196