[GlobalISel][AArch64] Handle tail calls with non-void return types

Just return once you emit the call, which is exactly what SelectionDAG does in
this situation.

Update call-translator-tail-call.ll.

Also update dllimport.ll to show that we tail call here in GISel again. Add
-verify-machineinstrs to the GISel line too, to defend against verifier
failures.

Differential revision: https://reviews.llvm.org/D67282

llvm-svn: 371425