drm/amdgpu:add switch buffer to end of CS (v2)

sync switch buffer scheme with windows kmd for gfx v8,
step1: append a switch_buffer to the end of CS

v2:rebase on latest staging

Signed-off-by: Monk Liu <Monk.Liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
index f5810f7..11f2fba 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
@@ -210,6 +210,8 @@
 		amdgpu_ring_patch_cond_exec(ring, patch_offset);
 
 	ring->current_ctx = ctx;
+	if (ring->funcs->emit_switch_buffer)
+		amdgpu_ring_emit_switch_buffer(ring);
 	amdgpu_ring_commit(ring);
 	return 0;
 }