[ARM] Refactor Thumb2 mul instruction descs

No functional changes. Just created wrapper classes around the 3
and 4 reg mult and mac instruction classes.

Differential Revision: http://reviews.llvm.org/D21549



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@274347 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed