realtek: debounce reset key for Zyxel GS1900

realtek: debounce reset key for Zyxel GS1900

When the reset button is next to the SFP cages, I2C operations on the
modules might cause interference on the button's GPIO line. Add a
debounce-interval of 5 times the poll-interval to ensure the line is
actually stable for some time and not just glitching.

This squashes commit 4357f32d41eb ("realtek: debounce reset key for
Zyxel GS1900") and commit 777c6106ed4e ("realtek: move debounce-interval
to correct node").

Signed-off-by: Sander Vanheule <sander@svanheule.net>