gpio: ep93xx: use handle_bad_irq() as default IRQ handler

gpio: ep93xx: use handle_bad_irq() as default IRQ handler

Replace the temporary fallback handle_simple_irq with handle_bad_irq
now that the driver operates with a proper hierarchical IRQ setup.
This ensures unexpected or unmapped interrupts are clearly flagged
instead of being silently handled.

Signed-off-by: Mohamed Ayman <mohamedaymanworkspace@gmail.com>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Link: https://patch.msgid.link/20260424115920.54707-1-mohamedaymanworkspace@gmail.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>