ARM: fix vectorized division on WoA

The Windows on ARM target uses custom division for normal division as
the backend needs to insert division-by-zero checks.  However, it is
designed to only handle non-vectorized division.  ARM has custom
lowering for vectorized division as that can avoid loading registers
with the values and invoke a division routine for each one, preferring
to lower using NEON instructions.  Fall back to the custom lowering for
the NEON instructions if we encounter a vectorized division.

Resolves PR31778!

llvm-svn: 293259