[LoongArch] Add LSX intrinsic support

For handling intrinsics, our approach is not simply to match them
one-to-one with instructions. Instead, we lower some intrinsics
to common nodes and then perform matching. The advantage of this
approach is that it allows us to fully utilize the passes available
at the common layer for optimizing purposes.

We perform error checks on the immediate operand of all intrinsics,
rather than waiting until the end to throw exceptions.

Reviewed By: SixWeining

Differential Revision: https://reviews.llvm.org/D155829