gpio: mvebu: Use the proper APIs

gpio: mvebu: Use the proper APIs

The MVEBU driver is requesting GPIO descriptors from itself, which
is fine, but we have proper APIs to do this in a controlled way, so
stop calling into the private functions of the GPIO library and use
the gpiochip_* functions instead. Only include <linux/gpio/driver.h>
and <linux/gpio/consumer.h> since we are both producers and consumers
in this case.

Cc: Gregory CLEMENT <gregory.clement@free-electrons.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>