ath79: calibrate nand netgear wndrxxxx with nvmem

ath79: calibrate nand netgear wndrxxxx with nvmem

Driver for both soc (2.4GHz Wifi) and pci (5 GHz) now pull the calibration
data from the nvmem subsystem.

This allows us to move the userspace caldata extraction for the pci-e ath9k
supported wifi into the device-tree definition of the device.

wmac's nodes are also changed over to use nvmem-cells over OpenWrt's
custom mtd-cal-data property.

The wifi mac address remains correct after these changes, because When both
"mac-address" and "calibration" are defined, the effective mac address
comes from the cell corresponding to "mac-address" and
mac-address-increment.

Test passed on my wndr3700v4 and wndr4500v3.
Signed-off-by: Edward Chow <equu@openmail.cc>