gpio: ep93xx: Fix single irqchip with multi gpiochips

Fixes the following warnings which results in interrupts disabled on
port B/F:

gpio gpiochip1: (B): detected irqchip that is shared with multiple gpiochips: please fix the driver.
gpio gpiochip5: (F): detected irqchip that is shared with multiple gpiochips: please fix the driver.

- added separate irqchip for each interrupt capable gpiochip
- provided unique names for each irqchip

Fixes: d2b09196 ("gpio: ep93xx: Pass irqchip when adding gpiochip")
Cc: <stable@vger.kernel.org>
Signed-off-by: Nikita Shubin <nikita.shubin@maquefel.me>
Tested-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>