avr32: use gpio_is_valid() to check USBA vbus_pin I/O line

This patch will use gpio_is_valid() to check the vbus_pin I/O line.
Signed-off-by: NHans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>
Signed-off-by: NHaavard Skinnemoen <haavard.skinnemoen@atmel.com>

arch/avr32/mach-at32ap/at32ap700x.c

@@ -1753,7 +1753,7 @@ at32_add_device_usba(unsigned int id, struct usba_platform_data *data)
 	if (platform_device_add_data(pdev, data, sizeof(usba_data)))
 		goto out_free_pdev;
 
-	if (data->vbus_pin >= 0)
+	if (gpio_is_valid(data->vbus_pin))
 		at32_select_gpio(data->vbus_pin, 0);
 
 	usba0_pclk.dev = &pdev->dev;