[NVPTX] Add NVPTX intrinsics for CUDA PTX 6.5 ldmatrix instructions

Adds NVPTX intrinsics for the CUDA PTX `ldmatrix.sync.aligned` instructions added in PTX 6.5.

PTX ISA description of `ldmatrix.sync.aligned`: https://docs.nvidia.com/cuda/parallel-thread-execution/index.html#warp-level-matrix-instructions-ldmatrix



Authored-by: Steffen Larsen <steffen.larsen@codeplay.com>

Reviewed By: tra

Differential Revision: https://reviews.llvm.org/D107046