backlight: Add Sanyo LV5207LP backlight driver

The LV5207LP is a multi-purpose 7 LEDs driver for the mobile market.
Only the main LED is supported by this driver.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>