mfd: mfd_cell is now implicitly available to timberdale drivers

The cell's platform_data is now accessed with a helper function;
change clients to use that, and remove the now-unused data_size.

Note that the mfd's platform_data is marked __devinitdata.  This
is still correct in all cases except for the timbgpio driver, whose
remove hook has been changed to no longer reference the pdata.

Signed-off-by: Andres Salomon <dilinger@queued.net>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>