drm/rockchip: vop2: Don't crash for invalid duplicate_state

It's possible for users to try to duplicate the CRTC state even when the
state doesn't exist. drm_atomic_helper_crtc_duplicate_state() (and other
users of __drm_atomic_helper_crtc_duplicate_state()) already guard this
with a WARN_ON() instead of crashing, so let's do that here too.

Fixes: 604be855 ("drm/rockchip: Add VOP2 driver")
Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20230621223311.2239547-5-jonas@kwiboo.se

drivers/gpu/drm/rockchip/rockchip_drm_vop2.c

@@ -2098,11 +2098,13 @@ static void vop2_crtc_reset(struct drm_crtc *crtc)
 
 static struct drm_crtc_state *vop2_crtc_duplicate_state(struct drm_crtc *crtc)
 {
-	struct rockchip_crtc_state *vcstate, *old_vcstate;
+	struct rockchip_crtc_state *vcstate;
 
-	old_vcstate = to_rockchip_crtc_state(crtc->state);
+	if (WARN_ON(!crtc->state))
+		return NULL;
 
-	vcstate = kmemdup(old_vcstate, sizeof(*old_vcstate), GFP_KERNEL);
+	vcstate = kmemdup(to_rockchip_crtc_state(crtc->state),
+			  sizeof(*vcstate), GFP_KERNEL);
 	if (!vcstate)
 		return NULL;