drm/amd/display: Use drm_fb_helper_poll_changed()

This driver can use drm_fb_helper_output_poll_changed() as its
.output_poll_changed callback.

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -792,7 +792,7 @@ dm_atomic_state_alloc_free(struct drm_atomic_state *state)
 
 static const struct drm_mode_config_funcs amdgpu_dm_mode_funcs = {
 	.fb_create = amdgpu_user_framebuffer_create,
-	.output_poll_changed = amdgpu_output_poll_changed,
+	.output_poll_changed = drm_fb_helper_output_poll_changed,
 	.atomic_check = amdgpu_dm_atomic_check,
 	.atomic_commit = amdgpu_dm_atomic_commit,
 	.atomic_state_alloc = dm_atomic_state_alloc,