[ARM][FIX] Add missing f16.lane.vldN/vstN lowering

Summary:
Add missing D and Q lane VLDSTLane lowering
for fp16 elements.

Reviewers: efriedma, kosarev, SjoerdMeijer, ostannard

Reviewed By: efriedma

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60874

llvm-svn: 358962