mtd-mac-address should no longer be used after commit 5ae2e78639
("kernel: drop support for mtd-mac-address"). Convert it to nvmem-cells.
While at it, also convert OpenWrt's custom mtd-cal-data property and
userspace pre-calibration data extraction to the nvmem implementation.
Note: nvmem-cells in QCN5502 wmac has not been tested.
Fixes: c32008a37b ("ath79: add partial support for Netgear EX7300v2")
Signed-off-by: Sungbo Eo <mans0n@gorani.run>
3e3e78de11