Out of all devices currently supported based on AR9331 chipset,
this one had the 'serial0' alias missing. Add it to fix setting of
/dev/console and login shell on the onboard UART.
Signed-off-by: Lech Perczak <lech.perczak@gmail.com>
(cherry picked from commit 94f344997769a9a18e2d73574d9d17785828955d)