kernel: select kmod-backlight as dependency for kmod-drm

Select kmod-backlight as dependency for kmod-drm in case kmod-backlight
is compiled.

This fixes kernel 5.10 build issues on x86-geode with all kmods
enabled:

Package kmod-drm is missing dependencies for the following libraries:
backlight.ko

Signed-off-by: David Bauer <[email protected]>

package/kernel/linux/modules/video.mk

@@ -225,7 +225,7 @@ define KernelPackage/drm
   SUBMENU:=$(VIDEO_MENU)
   TITLE:=Direct Rendering Manager (DRM) support
   HIDDEN:=1
-  DEPENDS:=+kmod-dma-buf +kmod-i2c-core
+  DEPENDS:=+kmod-dma-buf +kmod-i2c-core +PACKAGE_kmod-backlight:kmod-backlight
   KCONFIG:=CONFIG_DRM
   FILES:= \
 	$(LINUX_DIR)/drivers/gpu/drm/drm.ko \