gpio: implement bus_setup_intr and bus_teardown_intr

Implement bus_setup_intr and bus_teardown_intr as bus_generic_setup_intr
and bus_generic_teardown_intr respectively for GPIO drivers that support
interrupts. This allows children to setup interrupts.

Reported by: Evgenii Ivanov <devivanov@proton.me>
Reviewed by: imp
MFC after: 1 day
Differential Revision: https://reviews.freebsd.org/D52197