[mips] Modify long branch for NaCl:

  * Move the instruction that changes sp outside of the branch delay slot.
  * Bundle-align the target of indirect branch.

Differential Revision: http://llvm-reviews.chandlerc.com/D3928


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210262 91177308-0d34-0410-b5e6-96231b3b80d8