[mips] Fix 'jumpy' debug line info around calls.

Summary:
At the moment, address calculation is taking the debug line info from the
address node (e.g. TargetGlobalAddress). When a function is called multiple
times, this results in output of the form:

  .loc $first_call_location
  .. address calculation ..
  .. function call ..
  .. address calculation ..
  .loc $second_call_location
  .. function call ..
  .loc $first_call_location
  .. address calculation ..
  .loc $third_call_location
  .. function call ..

This patch makes address calculations for function calls take the debug line
info for the call node and results in output of the form:
  .loc $first_call_location
  .. address calculation ..
  .. function call ..
  .loc $second_call_location
  .. address calculation ..
  .. function call ..
  .loc $third_call_location
  .. address calculation ..
  .. function call ..

All other address calculations continue to use the address node.

Test Plan: Fixes test/DebugInfo/multiline.ll on a mips host.

Subscribers: dblaikie, llvm-commits

Differential Revision: http://reviews.llvm.org/D7050

llvm-svn: 227005