rampis: fix Reference to non-existent node for GB-PC2
Fix cannot build: Reference to non-existent node or label
"macaddr_factory_e000" dtb compilation error.
The cherry-pick had to be reworked to use the old mtd-mac-address way as
openwrt-21.02 still wasn't migrated to nvmem implementation.
Fixes: d604032c2a50 ("ramips: fix GB-PC1 and GB-PC2 device support")
Fixes: #11654
Fixes: #11385
Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
[ rework commit message, add more fixes tag ]
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>