backlight: l4f00242t03: Convert to GPIO descriptors

This converts the l4f00242t03 backlight driver to use GPIO
descriptors and switches the two Freescale i.MX boards over
to passing descriptors instead of global GPIO numbers.

We use the typical names "enable" and "reset" as found in
the device tree bindings for panel GPIOs.

This saves a lot of code in the driver and makes it possible
to get rid of the platform data header altogether.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Acked-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>