staging: olpc_dcon: add a missing dependency

  WARNING: unmet direct dependencies detected for BACKLIGHT_CLASS_DEVICE
    Depends on [n]: HAS_IOMEM [=y] && BACKLIGHT_LCD_SUPPORT [=n]
    Selected by [y]:
    - FB_OLPC_DCON [=y] && STAGING [=y] && X86 [=y] && OLPC [=y] && FB [=y]
                        && I2C [=y] && (GPIO_CS5535 [=n] || GPIO_CS5535 [=n]=n)

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/olpc_dcon/Kconfig

@@ -2,6 +2,7 @@ config FB_OLPC_DCON
 	tristate "One Laptop Per Child Display CONtroller support"
 	depends on OLPC && FB
 	depends on I2C
+	depends on BACKLIGHT_LCD_SUPPORT
 	depends on (GPIO_CS5535 || GPIO_CS5535=n)
 	select BACKLIGHT_CLASS_DEVICE
 	help