drm/vc4: hdmi: Fix pointer dereference before check

Commit 6bed2ea3 ("drm/vc4: hdmi: Reset link on hotplug") introduced
the vc4_hdmi_reset_link() function. This function dereferences the
"connector" pointer before checking whether it is NULL or not.

Rework variable assignment to avoid this issue.

Fixes: 6bed2ea3 ("drm/vc4: hdmi: Reset link on hotplug")
Signed-off-by: José Expósito <jose.exposito89@gmail.com>
Link: https://lore.kernel.org/r/20221110134752.238820-3-jose.exposito89@gmail.comSigned-off-by: Maxime Ripard <maxime@cerno.tech>

drivers/gpu/drm/vc4/vc4_hdmi.c

@@ -318,8 +318,8 @@ static int reset_pipe(struct drm_crtc *crtc,
 static int vc4_hdmi_reset_link(struct drm_connector *connector,
 			       struct drm_modeset_acquire_ctx *ctx)
 {
-	struct drm_device *drm = connector->dev;
-	struct vc4_hdmi *vc4_hdmi = connector_to_vc4_hdmi(connector);
+	struct drm_device *drm;
+	struct vc4_hdmi *vc4_hdmi;
 	struct drm_connector_state *conn_state;
 	struct drm_crtc_state *crtc_state;
 	struct drm_crtc *crtc;
@@ -330,6 +330,7 @@ static int vc4_hdmi_reset_link(struct drm_connector *connector,
 	if (!connector)
 		return 0;
 
+	drm = connector->dev;
 	ret = drm_modeset_lock(&drm->mode_config.connection_mutex, ctx);
 	if (ret)
 		return ret;
@@ -347,6 +348,7 @@ static int vc4_hdmi_reset_link(struct drm_connector *connector,
 	if (!crtc_state->active)
 		return 0;
 
+	vc4_hdmi = connector_to_vc4_hdmi(connector);
 	if (!vc4_hdmi_supports_scrambling(vc4_hdmi))
 		return 0;