[Clang] Add AArch64 VCMLA LANE variants.

Authored by fhahn on Jan 5 2021, 7:53 AM.


[Clang] Add AArch64 VCMLA LANE variants.

This patch adds the LANE variants for VCMLA on AArch64 as defined in
"Arm Neon Intrinsics Reference for ACLE Q3 2020" [1]

This patch also updates dup_typed to accept constant type strings directly.

Based on a patch by Tim Northover.

[1] https://developer.arm.com/documentation/ihi0073/latest

Reviewed By: SjoerdMeijer

Differential Revision: https://reviews.llvm.org/D93014