[X86] Add CRC32 feature.

d8faf038 implemented general-regs-only for X86 by disabling all features
with vector instructions. But the CRC32 instruction in SSE4.2 ISA, which uses
only GPRs, also becomes unavailable. This patch adds a CRC32 feature for this
instruction and allows it to be used with general-regs-only.

Reviewed By: pengfei

Differential Revision: https://reviews.llvm.org/D105462