[mips][XRay] Use the base version of emitXRayTable

Follow up rL290858 by removing the MIPS specific version of XRayTable
emission in favour of the basic version.

This resolves a buildbot failure where the ELF sections were malformed
causing the linker to reject the object files with xray related sections.

Reviewers: dberris, slthakur

Differential Revision: https://reviews.llvm.org/D32808

llvm-svn: 302138