Allow negative immediates in ARM and Thumb2 compares.

ARM and Thumb2 mode can use cmn instructions to compare against negative
immediates. Thumb1 mode can't.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154183 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed