arm: mvebu: turris_mox: Always handle reset button

Handle reset button even if we can't configure modules.

This happens if we fail retrieving reset GPIO with which we can reset
the modules.

(Note that this GPIO is different from reset button GPIO.)

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>