[mips] Extend ParseJumpTarget to support the full symbol expression syntax.

Summary:
This should fix the issues the D3222 caused in lld. Testcase is based on
the one that failed in the buildbot.

Depends on D3233

Reviewers: matheusalmeida, vmedic

Reviewed By: matheusalmeida

Differential Revision: http://llvm-reviews.chandlerc.com/D3234