AArch64: use less cluttered intrinsic for vtbl/vtbx

The table is always 128-bit so there's no reason to specify it every time we
want the intrinsic.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@202259 91177308-0d34-0410-b5e6-96231b3b80d8