sun8i: h3: NanoPi M1 Plus: Add emac configuration

NanoPi M1 plus have a 10/100/1000M ethernet with external phy.
Phy power is controlled by PD6.
Add the required configuration for it.

Signed-off-by: Emmanuel Vadot <manu@freebsd.org>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>