ARM: mvebu: Add a SOC bus device entry

Add the SoC Family, device ID and revision to /sys/bus/soc.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lkml.kernel.org/r/1393955507-26436-1-git-send-email-andrew@lunn.ch
Signed-off-by: Jason Cooper <jason@lakedaemon.net>