[GlobalISel][X86] Support G_LOAD/G_STORE i1.

Summary: Support G_LOAD/G_STORE i1.

Reviewers: zvi, guyblank

Reviewed By: guyblank

Subscribers: rovka, kristof.beyls, llvm-commits

Differential Revision: https://reviews.llvm.org/D35178

llvm-svn: 307527