drm/msm: Check for NULL before calling prepare_commit()

Add a NULL check before calling prepare_commit() in
msm_atomic_commit_tail()
Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Patchwork: https://patchwork.freedesktop.org/patch/523604/
Link: https://lore.kernel.org/r/20230221184256.1436-3-quic_jesszhan@quicinc.comSigned-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

drivers/gpu/drm/msm/msm_atomic.c

@@ -205,7 +205,8 @@ void msm_atomic_commit_tail(struct drm_atomic_state *state)
 	 * Now that there is no in-progress flush, prepare the
 	 * current update:
 	 */
-	kms->funcs->prepare_commit(kms, state);
+	if (kms->funcs->prepare_commit)
+		kms->funcs->prepare_commit(kms, state);
 
 	/*
 	 * Push atomic updates down to hardware: