[AArch64] Add lowering pattern for llvm.aarch64.neon.vcvtfxs2fp.f16.i64

Summary:  Add lowering pattern for llvm.aarch64.neon.vcvtfxs2fp.f16.i64

Reviewers: pbarrio, DavidSpickett, LukeGeeson

Reviewed By: LukeGeeson

Subscribers: javed.absar, kristof.beyls, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60259

llvm-svn: 358171