[mips] For indirect calls we don't need $gp to point to .got. Mips linker

[mips] For indirect calls we don't need $gp to point to .got.  Mips linker
doesn't generate lazy binding stub for a function whose address is taken in
the program.

Differential Revision: http://reviews.llvm.org/D5067

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218744 91177308-0d34-0410-b5e6-96231b3b80d8