OMAP: DSS2: Add Nokia DSI command mode panel configuration struct

Introduce a configuration struct for platform/board specific information
of Nokia DSI command mode panels, to be used in addition to struct
omap_dss_device (passed via the 'void *data' member).

Signed-off-by: Jani Nikula <ext-jani.1.nikula@nokia.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@nokia.com>