arm: mvebu: turris_omnia: Reset the board immediately on DDR training failure

The state of the current DDR training code for Armada 38x is such that
we cannot be sure it will always train successfully - although after the
last change we were yet unable to find a board that failed DDR training,
from experience in the last 2 years we know that it is possible.

The experience also tells us that in many cases the board fails training
only sometimes, and after a reset the training is successful.

Enable the new option that makes the board reset itself on DDR training
failure immediately. Until now we called hang() in such a case, which
meant that the board was reset by the MCU after 120 seconds.

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