locking.
- Break gpio_write into smaller sub-functions.
- Remove useless breaks after returns.
- Don't perform any change in IO_CFG_WRITE_MODE if values are invalid.
  (previously values were set and then set to zero)
- Change cast for copy_to_user to (void __user *)
- Make file_operations gpio_fops static and const.
- Make setget_output static. (However, it's still inline since the CRIS
  architecture is still not SMP, which makes the function small enough
  to inline)