gpio: ep93xx: split device in multiple

gpio: ep93xx: split device in multiple

This prepares ep93xx SOC gpio to convert into device tree driver:
- dropped banks and legacy defines
- split AB IRQ and make it shared

We are relying on IRQ number information A, B ports have single shared
IRQ, while F port have dedicated IRQ for each line.

Also we had to split single ep93xx platform_device into multiple, one
for each port, without this we can't do a full working transition from
legacy platform code into device tree capable. All GPIO_LOOKUP were
change to match new chip namings.

Signed-off-by: Nikita Shubin <nikita.shubin@maquefel.me>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>