We were not resetting the pointer to the associated gpio_device once
we are done displaying a pin's information.

This meant that once we reached the end of a gpio-range, if there
were pins right after it that did not belong to any known range,
they would be associated with the previous range's gpio device.

This resulted in those pins appearing as <4294966783:old_gdev> instead
of the expected <0:?> (due to gpio_num being -1).
Signed-off-by: Léo DUBOIN <lduboin@freebox.fr>
Link: https://lore.kernel.org/r/c40d0634abefa19e689ffd450e0f48a8d63c4fc4.1714049455.git.lduboin@freebox.frSigned-off-by: Linus Walleij <linus.walleij@linaro.org>