uboot-imx

gpio: at91_gpio: remove CPU_HAS_PIO3 macro

The intention of the removal is the preparation to introduce the
new AT91 PIO pinctrl driver.

Use the union to make the PIO3 and PIO2's registers be together
and make their offset aligned.

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Reviewed-by: Simon Glass <sjg@chromium.org>