Documentation: firmware-guide: gpio-properties: active_low only for GpioIo()

It appears that people may misinterpret active_low field in _DSD
for GpioInt() resource. Add a paragraph to clarify this.

Reported-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: andy-shev

Documentation/firmware-guide/acpi/gpio-properties.rst

@@ -55,6 +55,9 @@ Since ACPI GpioIo() resource does not have a field saying whether it is
 active low or high, the "active_low" argument can be used here.  Setting
 it to 1 marks the GPIO as active low.
 
+Note, active_low in _DSD does not make sense for GpioInt() resource and
+must be 0. GpioInt() resource has its own means of defining it.
+
 In our Bluetooth example the "reset-gpios" refers to the second GpioIo()
 resource, second pin in that resource with the GPIO number of 31.