Use mfd_data for passing information from mfd drivers to soc
clients.  The mfd_cell's driver_data field is being phased out.

Clients that were using driver_data now access .mfd_data
via mfd_get_data().
Signed-off-by: NAndres Salomon <dilinger@queued.net>
Acked-by: NMark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: NSamuel Ortiz <sameo@linux.intel.com>