CodeGen: enable mov.w/mov.t pairs with minsize for WoA

Windows on ARM uses COFF/PE which is intrinsically position independent.  For
the case of 32-bit immediates, use a pair-wise relocation as otherwise we may
exceed the range of operators.  This fixes a code generation crash when using
-Oz when targeting Windows on ARM.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210814 91177308-0d34-0410-b5e6-96231b3b80d8