arm: mvebu: turris_mox: start blinking PHY LEDs when entering rescue

Configure blinking on ethernet PHY LEDs on the MOX A board when entering
rescue mode via reset button.

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