[mips] Expansion of BEQL and BNEL with immediate operands

Adds support for BEQL and BNEL macros with immediate operands.

Patch by: Srdjan Obucina

Reviewers: dsanders, zoran.jovanovic, vkalintiris, sdardis, obucina, seanbruno

Differential Revision: https://reviews.llvm.org/D17040

llvm-svn: 293905