leds: pca955x: Include the right GPIO header

This driver provides a GPIO chip, so include <linux/gpio/driver.h>
and not the legacy <linux/gpio.h> header.

Cc: Andrew Jeffery <andrew@aj.id.au>
Cc: Joel Stanley <joel@jms.id.au>
Cc: Matt Spinler <mspinler@linux.vnet.ibm.com>
Cc: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Pavel Machek <pavel@ucw.cz>