ath79: fix dtc warnings in eap1750h

ath79: fix dtc warnings in eap1750h

|109.3-19: Warning (reg_format): macaddr@0:reg:property has invalid length (8 bytes)
|113.3-24: Warning (reg_format): calibration@1000:reg: property has invalid length (8 bytes)
|117.3-24: Warning (reg_format): calibration@5000:reg: property has invalid length (8 bytes)

also integrate the art-nodes nodes back into the partition-subnode
and change the calibration labels to match what everyone else is
doing.

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>