drm/hisilicon/hibmc: fix 'xset dpms force off' fail

both crtc_state->adjusted_mode.hdisplay and
crtc_state->adjusted_mode.vdisplay are 0 when switch dpms off,
return -EINVAL cause switch dpms off fail.
Signed-off-by: Zhihui Chen <chenzhihui4@huawei.com>
Signed-off-by: Xinliang Liu <xinliang.liu@linaro.org>
Acked-by: Xinliang Liu <xinliang.liu@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191220023004.2658-1-chenzhihui4@huawei.com

drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_de.c

@@ -80,6 +80,9 @@ static int hibmc_plane_atomic_check(struct drm_plane *plane,
 		return -EINVAL;
 	}
 
+	if (!crtc_state->enable)
+		return 0;
+
 	if (state->crtc_x + state->crtc_w >
 	    crtc_state->adjusted_mode.hdisplay ||
 	    state->crtc_y + state->crtc_h >