pinctrl: baytrail: Add pin control operations

Add implementation for:
- pin control, group information retrieval: count, name and pins
- pin muxing:
  - function information (count, name and groups)
  - mux setting
  - gpio control (enable, disable, set direction)
- pin configuration:
  - pull disable
  - pull up/down and pull strength
  - debounce
  - any other option is treated as not supported.

Signed-off-by: Cristina Ciocan <cristina.ciocan@intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>