pinctrl: intel: Get rid of unused members in struct intel_function

The driver has been converted to a generic data type and macro for
the pin function definition, hence get rid of not used members in
the struct intel_function.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>