gpio: Add support for push-pull/open-drain output mode

This attribute is not part of gpio standard attributes
so it's necessary to implement a custom version of this function

Signed-off-by: Nicola Ponte <nicola.ponte@u-blox.com>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

src/gpio/gpio.c

@@ -881,3 +881,20 @@ mraa_gpio_input_mode(mraa_gpio_context dev, mraa_gpio_input_mode_t mode)
 
     return MRAA_SUCCESS;
 }
+
+
+mraa_result_t
+mraa_gpio_out_driver_mode(mraa_gpio_context dev, mraa_gpio_out_driver_mode_t mode)
+{
+    if (dev == NULL) {
+        syslog(LOG_ERR, "gpio: write: context is invalid");
+        return MRAA_ERROR_INVALID_HANDLE;
+    }
+
+    if (IS_FUNC_DEFINED(dev, gpio_out_driver_mode_replace)) {
+        return dev->advance_func->gpio_out_driver_mode_replace(dev, mode);
+    }
+    else {
+        return MRAA_ERROR_FEATURE_NOT_SUPPORTED;
+    }
+}