[ARM] Materialise some boolean values to avoid a branch

This patch combines some cases of ARMISD::CMOV for integers that arise in comparisons of the form

  a != b ? x : 0
  a == b ? 0 : x

and that currently (e.g. in Thumb1) are emitted as branches.

Differential Revision: https://reviews.llvm.org/D34515

llvm-svn: 325323