New version of the PCU firmware supports two new commands:
  - IMS_PCU_CMD_OFN_SET_CONFIG which allows to write data to the
  registers of one finger navigation(OFN) chip present on the device
  - IMS_PCU_CMD_OFN_GET_CONFIG which allows to read data form the
  registers of said chip.

This commit adds two helper functions to use those commands and sysfs
attributes to use them. It also exposes some OFN configuration
parameters via sysfs.
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>