Unlike LCD type information, IP address as well as netmaks are not
stored in an easily usable format in RAVE SP EEPROM. In order to obtain
them we need to issue a special command to RAVE SP. For that purpose add
device "sp" and expose that data as a device parameters (sp.ipaddr and
sp.netmask, correspondingly)

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>