Filter AUX key bouncing

Filter AUX key bouncing

This patch filters AUX key bouncing. We store the state of
the AUX button and only change it when we notice that at
least AUX_TIMER_CONSECUTIVE_EVENTS consecutive equal GPIO
reads occur.

This should solve #2185 (AUX button makes interrupt storm)
but we still need the confirmation from someone affected by
the IRQ storm. In my test setup I could see an improvement
but I would only get 1 unwanted IRQ.

The next step is to use the same timer for more keys. For
that we could use the neo1973kbd_default_key_irq function
for the AUX key also.

Signed-off-by: Nelson Castillo <arhuaco@freaks-unidos.net>