[AArch64][FastISel] Handle CRC32 intrinsics

With a similar reason as D148023; some applications make heavy use of
the CRC32 intrinsic (e.g., as part of a hash function) and therefore
benefit from avoiding frequent SelectionDAG fallbacks. In our
application, we get a 2% compile-time improvement.

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D148917