gpio/at91: auto request and configure the pio as input when the interrupt is used via DT

If we do this

	interrupt-parent = <&pioA>;
	interrupts = <7 0x0>;

The current core map the irq correctly but the gpio is not configured as input.
The pinctrl configure the pin as gpio with the correct mux parameter but is
not responsible to configure it as input.

So do it during the xlate

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>