pinctrl: intel: Introduce new flag to force GPIO base to be 0

pinctrl: intel: Introduce new flag to force GPIO base to be 0

In some cases not the first group would like to have GPIO base to be 0.
It's not possible right now due to 0 has special meaning already. Thus,
introduce a new flag to allow drivers to force GPIO base to be 0 on
a certain group. It's assumed that it can be only one group per device
with such flag enabled.

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