Use mfd_data for passing information from mfd drivers to mfd
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().  This changes ds1wm only; mfd drivers with
other cells are not modified, with the exception of led_cell.

The led_cell.driver_data line is dropped from htc-pasic3.c in this
patch as well.  It's not used in mainline (there's no leds-pasic3
platform driver), so it should be safe to take care of that here.
Signed-off-by: Andres Salomon <dilinger@queued.net>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>