No need to explicitly set the cell's platform_data/data_size.

Modify clients to use mfd_get_cell helper function instead of
accessing platform_data directly.
Signed-off-by: NAndres Salomon <dilinger@queued.net>
Acked-by: NJean Delvare <khali@linux-fr.org>
Signed-off-by: NSamuel Ortiz <sameo@linux.intel.com>