drivers: gpio: sch: implementation does not configure interrupt level/edge

`gpio_sch.c` configures for interrupts but does not inspect the trigger type (`GPIO_INT_LEVEL` vs `GPIO_INT_EDGE`).  It should do so and should diagnose if one of those triggers is not supported.

As implemented the driver will behave correctly only for level-triggered interrupts (`GPIO_INT_EDGE` is the non-default configuration).