[AMDGPU]  Return true in enableMultipleCopyHints().

Enable multiple COPY hints to eliminate more COPYs during register allocation.

Note that this is something all targets should do, see
https://reviews.llvm.org/D38128.

Review: Stanislav Mekhanoshin, Tom Stellard.
llvm-svn: 325425
diff --git a/llvm/test/CodeGen/AMDGPU/callee-special-input-vgprs.ll b/llvm/test/CodeGen/AMDGPU/callee-special-input-vgprs.ll
index 13cb8b5..25c40dd 100644
--- a/llvm/test/CodeGen/AMDGPU/callee-special-input-vgprs.ll
+++ b/llvm/test/CodeGen/AMDGPU/callee-special-input-vgprs.ll
@@ -220,8 +220,8 @@
 ; GCN-LABEL: {{^}}kern_indirect_other_arg_use_workitem_id_z:
 ; GCN: enable_vgpr_workitem_id = 2
 
-; GCN: v_mov_b32_e32 v0, 0x22b
-; GCN: v_mov_b32_e32 v1, v2
+; GCN-DAG: v_mov_b32_e32 v0, 0x22b
+; GCN-DAG: v_mov_b32_e32 v1, v2
 ; GCN: s_swappc_b64
 ; GCN-NOT: v0
 define amdgpu_kernel void @kern_indirect_other_arg_use_workitem_id_z() #1 {