This driver is just using <gpio/driver.h> so include that and
not the legacy <linux/gpio.h> header.

Cc: Antti Palosaari <crope@iki.fi>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>