arm64: dts: ls1028a: sl28: keep switch port names consistent

Keep the switch port labels consistent across the different board
variants. If the user wants to rename them, it should be done in
user-space.

Fixes: ab43f030 ("arm64: dts: ls1028a: sl28: add support for variant 2")
Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>