[AArch64]Fix the problem can't select f16_to_f32 and f32_to_f16.
Also add copy support for FPR16.
Also add a missing test case file belongs to commit r197361.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199463 91177308-0d34-0410-b5e6-96231b3b80d8
Replace duplicated code with a existing helper function.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199468 91177308-0d34-0410-b5e6-96231b3b80d8