video: backlight: Remove useless BACKLIGHT_LCD_SUPPORT kernel symbol

We have two *_CLASS_DEVICE kernel config options (LCD_CLASS_DEVICE
and BACKLIGHT_LCD_DEVICE) that do the same job.
The patch removes useless BACKLIGHT_LCD_SUPPORT option
and converts LCD_CLASS_DEVICE into a menu.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>