gpio: sysfs: emit chardev line-state events on edge store

In order to emit line-state events on edge changes in sysfs, update the
EDGE flags in the descriptor in gpio_sysfs_request_irq() and emit the
event on a successful store.

Reviewed-by: Kent Gibson <warthog618@gmail.com>
Link: https://lore.kernel.org/r/20241031-gpio-notify-sysfs-v4-5-142021c2195c@linaro.org


Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>