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>

drivers/pinctrl/intel/pinctrl-intel.h

@@ -70,10 +70,12 @@ struct intel_padgroup {
 /**
  * enum - Special treatment for GPIO base in pad group
  *
+ * @INTEL_GPIO_BASE_ZERO:	force GPIO base to be 0
  * @INTEL_GPIO_BASE_NOMAP:	no GPIO mapping should be created
  * @INTEL_GPIO_BASE_MATCH:	matches with starting pin number
  */
 enum {
+	INTEL_GPIO_BASE_ZERO	= -2,
 	INTEL_GPIO_BASE_NOMAP	= -1,
 	INTEL_GPIO_BASE_MATCH	= 0,
 };