pinctrl: lynxpoint: Assume 2 bits for mode selector

New generations can use 2 bits for mode selector.
Update the code to support it.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>