In lantiq there are several subtarget where all devices have the
same value set to the SOC variable for each device individually.
This patch introduces a non-device-dependent variable DEFAULT_SOC,
which is used if no specific SOC is set for a device, and thus reduces
the number of redundant definitions drastically.
This is applied to all subtargets except xway, as only the latter has
two different SOCs.
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
09ee51c614