staging: greybus: remove completed GPIO conversion task from TODO

staging: greybus: remove completed GPIO conversion task from TODO

The task to convert the Greybus subsystem to the GPIO descriptor
interface has been completed. A grep of the directory confirms that
no consumer drivers include <linux/gpio.h> or use the legacy integer
based GPIO API (gpio_request, gpio_set_value, etc).

Remove the stale entry from the TODO file.

Signed-off-by: Archit Anant <architanant5@gmail.com>
Link: https://patch.msgid.link/20260124174149.10314-1-architanant5@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>