drm/panel: himax-hx83102: Add a check to prevent NULL pointer dereference

drm_mode_duplicate() could return NULL due to lack of memory,
which will then call NULL pointer dereference. Add a check to
prevent it.

Fixes: 0ef94554dc40 ("drm/panel: himax-hx83102: Break out as separate driver")
Signed-off-by: Zhang Zekun <[e-mail]>
Reviewed-by: Neil Armstrong <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Neil Armstrong <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/panel/panel-himax-hx83102.c

···
 	struct drm_display_mode *mode;
 
 	mode = drm_mode_duplicate(connector->dev, m);
+	if (!mode)
+		return -ENOMEM;
 
 	mode->type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
 	drm_mode_set_name(mode);