pinctrl: intel: Allow to request locked pads

Some firmwares would like to protect pads from being modified by OS
and at the same time provide them to OS as a resource. So, the driver
in such circumstances may request pad and may not change its state.

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