ARM: mvebu: remove aliases for Ethernet devices on Armada 370/375/38x/XP

Having aliases for Ethernet devices is useless, since the networking
subsystem unfortunately doesn't care about aliases to name network
interfaces.

Note that the 'aliases' nodes in armada-370-xp.dtsi and armada-xp.dtsi
become empty, but that we keep it as is since a followup patch will
re-add some aliases to it.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>