[GlobalISel]: Create VREGs for ConstantInt args

[GlobalISel]: Create VREGs for ConstantInt args

This patch changes the behavior of IRTranslating intrinsics where we
now create VREG + G_CONSTANT for ConstantInt values. We already do this
for FloatingPoint values. This makes it easier for the backends to
select code and it won't have to de-duplicate creation+selection of
constants.

Reviewed by: ab

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@298473 91177308-0d34-0410-b5e6-96231b3b80d8