UBUNTU: [Config] built in SMSC_PHY driver for fsl-imx51

BugLink: http://bugs.launchpad.net/bugs/457878

The on-board PHY device of Freescale Babbage board is SMSC LAN8700, which is
supported by this CONFIG_SMSC_PHY driver in phylib. Since phylib is already
enabled in fec.c driver, to build in this SMSC_PHY driver will give us better
supporting of the PHY device.

Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
Acked-by: Amit Kucheria <amit.kucheria@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>