Add RealView/EB support for the LAN9118 Ethernet chip

RealView/EB revD platform comes with the SMSC LAN9118 Ethernet
chip. This patch allows either the smc91x or the smc911x drivers to be
used with the RealView/EB platform.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>