[ARM] Prefer BIC over BFC in ARM mode.

[ARM] Prefer BIC over BFC in ARM mode.

BIC is generally faster, and it can put the output in a different
register from the input.

We already do this in Thumb2 mode; not sure why the equivalent fix
never got applied to ARM mode.

Differential Revision: https://reviews.llvm.org/D31797

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@299803 91177308-0d34-0410-b5e6-96231b3b80d8