[mips] Never select JAL for calls to an absolute immediate address.

Summary:
It actually takes an offset into the current PC-region.

This fixes the 'expr' command in lldb.

Reviewers: vkalintiris, jaydeep, bhushan

Subscribers: dsanders, llvm-commits

Differential Revision: http://reviews.llvm.org/D16054

llvm-svn: 257339