arm64: dts: ls1028a: sl28: get MAC addresses from VPD

Now that it is finally possible to get the MAC addresses from the OTP
memory, use it to set the addresses of the network devices.

There are 8 reserved MAC addresses in total per board. Distribute them
as follows:

+----------+------+------+------+------+------+
|          | var1 | var2 | var3 | var4 | kbox |
+----------+------+------+------+------+------+
| enetc #0 |   +0 |      |      |   +0 |   +0 |
| enetc #1 |      |      |   +0 |   +1 |   +1 |
| enetc #2 |      |   +2 |      |      |   +2 |
| enetc #3 |      |   +3 |      |      |   +3 |
| felix p0 |      |   +0 |      |      |   +4 |
| felix p1 |      |   +1 |      |      |   +5 |
| felix p2 |      |      |      |      |   +6 |
| felix p3 |      |      |      |      |   +7 |
| felix p4 |      |      |      |      |      |
| felix p5 |      |      |      |      |      |
+----------+------+------+------+------+------+

An empty cell means, the port is not available and thus doesn't need an
ethernet address.

Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>