Move the Ethernet node from the root of the device tree to the BSC node,
as it's connected to the Bus State Controller.  This allows the system
to know the right position of the Ethernet node in the clock and PM
domain hierarchy, and manage the clock and PM domain appropriately.

Also rename the node's name from "lan9220" to "ethernet", to conform to
ePAPR generic name recomendations.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>