[ARM] Don't omit non-default predication code

This was causing the (invalid) predicated versions of the NEON VRINTX and
VRINTZ instructions to be accepted, with the condition code being ignored.

Also, there is no NEON VRINTR instruction, so that part of the check was not
necessary.

Differential revision: https://reviews.llvm.org/D39193

llvm-svn: 318771