Force the alignment of LDS variable to 16bytes
Force the alignment of LDS variable to 16bytes

It seems LLVM back-end can't set alignment correctly for ds_read/write_b64 instructions.
we should force the alignment to 16 bytes.

googlestadia/llpc,googlestadia/llpc,googlestadia/llpc,GPUOpen-Drivers/llpc,GPUOpen-Drivers/llpc,GPUOpen-Drivers/llpc,googlestadia/llpc,GPUOpen-Drivers/llpc,googlestadia/llpc,GPUOpen-Drivers/llpc