[Aarch64] Add v8.2-a half precision element extract intrinsics

[Aarch64] Add v8.2-a half precision element extract intrinsics

Summary:
Implements the intrinsics define on the ACLE to extract half precision fp scalar elements from float16x4_t and float16x8_t vector types.
a.k.a:
vduph_lane_f16
vduph_laneq_f16

Reviewers: pablooliveira, olista01, LukeGeeson, DavidSpickett

Reviewed By: DavidSpickett

Subscribers: DavidSpickett, javed.absar, kristof.beyls, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D60272

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@358276 91177308-0d34-0410-b5e6-96231b3b80d8