arm/mgcoge3un: check dip_switch at startup

Similar to kmcoge5un we need to check the dip switch at startup
connected to the kirkwood at MPP43. If it's set we need to set the
actual_bank to zero to boot from SW bank zero. Additional to kmcoge5un
we need to check also the pin in misc_init to decide wether we wait for
the ne to start or not. If the dip_switch is set we don't wait and
continue immediately.

Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>