ARM: davinci_all_defconfig: enable SMSC ethernet PHY

The LCDK embeds a LAN8710.

Cc: Sekhar Nori <nsekhar@ti.com>
Cc: Kevin Hilman <khilman@baylibre.com>
Acked-by: Kevin Hilman <khilman@baylibre.com>
Tested-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Karl Beldan <kbeldan@baylibre.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>