ath79: remove further redundant mtd-mac-address for wmac

ath79: remove further redundant mtd-mac-address for wmac

For several devices, wmac MAC address is set from art 0x1002
explicitly by using mtd-mac-address although mtd-cal-data is
pulled from art 0x1000.

With the MAC address in 0x1002, the driver should automatically
use it when reading caldata from 0x1000. Thus, remove the
redundant mtd-mac-address for those devices.

This patch addresses the cases where the calibration data partition
is not labelled art, having been overlooked in the first patch.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>