usb: chipidea: udc: otg_set_peripheral is useless for some chipidea users

It is useless at below cases:
- If we implement both usb host and device at chipidea driver.
- If we don't need phy->otg.
Tested-by: NMarek Vasut <marex@denx.de>
Signed-off-by: NPeter Chen <peter.chen@freescale.com>
Signed-off-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/chipidea/udc.c

@@ -1805,7 +1805,12 @@ static int udc_start(struct ci_hdrc *ci)
 	if (ci->transceiver) {
 		retval = otg_set_peripheral(ci->transceiver->otg,
 						&ci->gadget);
-		if (retval)
+		/*
+		 * If we implement all USB functions using chipidea drivers,
+		 * it doesn't need to call above API, meanwhile, if we only
+		 * use gadget function, calling above API is useless.
+		 */
+		if (retval && retval != -ENOTSUPP)
 			goto put_transceiver;
 	}