[ARM] Code size optimisation to lower udiv+urem to udiv+mls instead of a

[ARM] Code size optimisation to lower udiv+urem to udiv+mls instead of a
library call to __aeabi_uidivmod. This is an improved implementation of
r280808, see also D24133, that got reverted because isel was stuck in a loop.
That was caused by the optimisation incorrectly triggering on i64 ints, which
shouldn't happen because there is no 64bit hwdiv support; that put isel's type
legalization and this optimisation in a loop. A native ARM compiler and testing
now shows that this is fixed.

Patch mostly by Pablo Barrio.

Differential Revision: https://reviews.llvm.org/D25077

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@283098 91177308-0d34-0410-b5e6-96231b3b80d8