Add v4f16 to supported value types.

This is useful for some ARM intrinsics such as VCVTN which does a <4 x float> <-> <4 x half> conversion.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191870 91177308-0d34-0410-b5e6-96231b3b80d8