[AArch64] Corrected FP16 Intrinsic range checks in Clang + added Sema tests

Summary:
This fixes the ranges for the vcvth family of FP16 intrinsics in the clang front end. Previously it was accepting incorrect ranges
-Changed builtin range checking in SemaChecking
-added tests SemaCheck changes - included in  their own file since no similar one exists
-modified existing tests to reflect new ranges

Reviewers: SjoerdMeijer, javed.absar

Reviewed By: SjoerdMeijer

Subscribers: kristof.beyls, cfe-commits

Differential Revision: https://reviews.llvm.org/D47592

llvm-svn: 334489