leds: lp3952: Include the right header

This driver is using the GPIO descriptor API properly
as it should be but is including the legacy GPIO header
<linux/gpio.h>. Fix it by including <linux/gpio/consumer.h>
instead.

Cc: Tony Makkiel <tony.makkiel@daqri.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Pavel Machek <pavel@ucw.cz>