sandbox: net: Add aliases for ethernet devices

Commit f3dd213e ("net: introduce helpers to get PHY ofnode from MAC")
changed the ethernet sequence assignment from

uclass 36: ethernet
0   * eth@10002000 @ 05813460, seq 0
1   * eth@10003000 @ 05813550, seq 5
2   * sbe5 @ 05813640, seq 3
3   * eth@10004000 @ 05813730, seq 6
4   * dsa-test-eth @ 05813820, seq 4
5   * lan0 @ 05813a30, seq 2
6   * lan1 @ 05813b50, seq 7

to

uclass 36: ethernet
0   * eth@10002000 @ 03813630, seq 0
1   * eth@10003000 @ 03813720, seq 5
2   * sbe5 @ 03813810, seq 3
3   * eth@10004000 @ 03813900, seq 6
4     phy-test-eth @ 038139f0, seq 7
5   * dsa-test-eth @ 03813ae0, seq 4
6   * lan0 @ 03813cf0, seq 2
7   * lan1 @ 03813e10, seq 8

This caused the mac address assignment to switch around. Avoid this in
the future by assigning aliases for all ethernet devices. This reverts
the sequence to what it was before the aformentioned commit (with
phy-test-eth as seq 8). There is no ethernet1 for whatever reason.

Signed-off-by: Sean Anderson <sean.anderson@seco.com>