drm: panel: visionox: add backlight dependency

The newly added driver uses the backlight subsystem but is missing the
corresponding Kconfig dependency:

arm-linux-gnueabi-ld: drivers/gpu/drm/panel/panel-visionox-vtdr6130.o: in function `visionox_vtdr6130_probe':
panel-visionox-vtdr6130.c:(.text+0xdee): undefined reference to `devm_backlight_device_register'

Fixes: 65dc9360 ("drm: panel: Add Himax HX8394 panel controller driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230117165522.2104380-1-arnd@kernel.org

drivers/gpu/drm/panel/Kconfig

@@ -742,6 +742,7 @@ config DRM_PANEL_VISIONOX_VTDR6130
 	tristate "Visionox VTDR6130"
 	depends on OF
 	depends on DRM_MIPI_DSI
+	depends on BACKLIGHT_CLASS_DEVICE
 	help
 	  Say Y here if you want to enable support for Visionox
 	  VTDR6130 1080x2400 AMOLED DSI panel.