SPEAr: Add macb driver support for spear310 and spear320

SPEAr310 and SPEAr320 SoCs have an extra ethernet controller. The
driver for this device is already supported by u-boot, so configuring
board configuration file and defining base addresses etc to make use
of the common driver

Signed-off-by: Vipin Kumar <vipin.kumar@st.com>
Signed-off-by: Amit Virdi <amit.virdi@st.com>
Signed-off-by: Stefan Roese <sr@denx.de>