gpio_keys module can either accept gpios or interrupts. The module
initializes delayed work in case of gpios only and is only used if
debounce timer is not used, so make sure cancel_delayed_work_sync()
is called only when its gpio-backed and debounce_use_hrtimer is false.
This fixes the issue seen below when the gpio_keys module is unloaded and
an interrupt pin is used instead of GPIO: