drm: always check the repaint_status in update_complete

Initially finish_frame() was never called in drm_output_update_complete() for
'dpms_off_pending = true'. This is wrong for repaint_status ==
REPAINT_AWAITING_COMPLETION and that was fixed in
68d49d772c ("compositor-drm: run finish_frame when
dpms is turned off in update_complete").
However finish_frame() may now be called for repaint_status !=
REPAINT_AWAITING_COMPLETION, which is not allowed and results in a failed
assertion.

Fix this by checking dpms and repaint_status unconditionally.

Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>

libweston/backend-drm/drm.c

@@ -306,7 +306,8 @@ drm_output_update_complete(struct drm_output *output, uint32_t flags,
 		output->dpms_off_pending = false;
 		drm_output_get_disable_state(pending, output);
 		drm_pending_state_apply_sync(pending);
-	} else if (output->state_cur->dpms == WESTON_DPMS_OFF &&
+	}
+	if (output->state_cur->dpms == WESTON_DPMS_OFF &&
 	    output->base.repaint_status != REPAINT_AWAITING_COMPLETION) {
 		/* DPMS can happen to us either in the middle of a repaint
 		 * cycle (when we have painted fresh content, only to throw it