drm: shmobile: fix Kconfig dependencies

The shmobile drm driver selects BACKLIGHT_CLASS_DEVICE as of 0a5a5499ad88 "drm: shmobile: Add dependency on BACKLIGHT_CLASS_DEVICE", but that option in turn depends on BACKLIGHT_LCD_SUPPORT, so we actually have to select both, or alternatively use 'depends on BACKLIGHT_CLASS_DEVICE'.

Further, the driver uses FB_SH_MOBILE_MERAM if that is enabled, but this breaks if MERAM is a module while the DRM driver is built-in. To solve this, add a dependency on "FB_SH_MOBILE_MERAM || !FB_SH_MOBILE_MERAM", which forces DRM_SHMOBILE to be a module if FB_SH_MOBILE_MERAM set to 'm'.

index a50fe0eeaa0d..8d17d00ddb4b 100644
@@ -2,7 +2,9 @@ config DRM_SHMOBILE
 	tristate "DRM Support for SH Mobile"
 	depends on DRM && ARM
 	depends on ARCH_SHMOBILE || COMPILE_TEST
+	depends on FB_SH_MOBILE_MERAM || !FB_SH_MOBILE_MERAM
 	select BACKLIGHT_CLASS_DEVICE
+	select BACKLIGHT_LCD_SUPPORT
 	select DRM_KMS_HELPER
 	select DRM_KMS_FB_HELPER
 	select DRM_KMS_CMA_HELPER