Don't use .arm for ARMv7M, which will use the hwdiv path. Non-hwdiv
remains ARM mode only, supporting thumb requires explicit it prefixes
for the predicted adds/subs and adjusting the offset computation for the
different block sizes.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@200035 91177308-0d34-0410-b5e6-96231b3b80d8