ath79: calibrate TP-LINK TL-WR2543ND with nvmem

Driver for and pci wlan card 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.

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 tplink tl-wr2543nd.

Signed-off-by: Edward Chow <equu@openmail.cc>