[AArch64][GlobalISel] Select llvm.aarch64.stlxr(i64, i64*)

This adds partial instruction selection support for llvm.aarch64.stlxr. It also
factors out selection for G_INTRINSIC_W_SIDE_EFFECTS into its own function. The
new function removes the restriction that the intrinsic ID on the
G_INTRINSIC_W_SIDE_EFFECTS be on operand 0.

Also add a test, and add a GISel line to arm64-ldxr-stxr.ll.

Differential Revision: https://reviews.llvm.org/D60100

llvm-svn: 357518