dt-bindings: doc: net: remove Linux API references

In commit 687e3d55 ("dt-bindings: doc: reflect new NVMEM
of_get_mac_address behaviour") I've kept or added references to Linux
of_get_mac_address API which is unwanted so this patch fixes that by
removing those references.

Fixes: 687e3d55

 ("dt-bindings: doc: reflect new NVMEM of_get_mac_address behaviour")
Suggested-by: Rob Herring <robh@kernel.org>
Signed-off-by: Petr Štetiar <ynezz@true.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>