gpio: mockup: increase the number of supported device properties

The driver actually supports 4 properties but we only ever set up up to
three. This will change however in upcoming patches so increase the
number of really (as in: the number the property array can hold)
supported properties to 4.
Reported-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/gpio/gpio-mockup.c

@@ -29,8 +29,8 @@
  * of GPIO lines.
  */
 #define GPIO_MOCKUP_MAX_RANGES	(GPIO_MOCKUP_MAX_GC * 2)
-/* Maximum of three properties + the sentinel. */
-#define GPIO_MOCKUP_MAX_PROP	4
+/* Maximum of four properties + the sentinel. */
+#define GPIO_MOCKUP_MAX_PROP	5
 
 /*
  * struct gpio_pin_status - structure describing a GPIO status