[X86][FastISel] Handle CRC32 intrinsics

Some applications make heavy use of the crc32 operation (e.g., as part
of a hash function), so having a FastISel path avoids fallbacks to
SelectionDAG and improves compile times, in our case by ~1.5%.

Reviewed By: pengfei

Differential Revision: https://reviews.llvm.org/D148023