rtc: omap: use of_device_is_system_power_controller function

Use of_device_is_system_power_controller instead of manually reading
the system-power-controller property from the device tree node.
Reviewed-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-omap.c

@@ -721,8 +721,7 @@ static int omap_rtc_probe(struct platform_device *pdev)
 	if (of_id) {
 		rtc->type = of_id->data;
 		rtc->is_pmic_controller = rtc->type->has_pmic_mode &&
-				of_property_read_bool(pdev->dev.of_node,
-						"system-power-controller");
+			of_device_is_system_power_controller(pdev->dev.of_node);
 	} else {
 		id_entry = platform_get_device_id(pdev);
 		rtc->type = (void *)id_entry->driver_data;