usb: musb: host: rely on port_mode to call musb_start()

Currently, we're calling musb_start() twice for DRD ports
in some situations. This has been observed to cause enumeration
issues after suspend/resume cycles with AM335x.

In order to fix the problem, we just have to fix the check
on musb_has_gadget() so that it only returns true if
current mode is Host and ignore the fact that we have or
not a gadget driver loaded.

Fixes: ae44df2e21b5 (usb: musb: call musb_start() only once in OTG mode)
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: <stable@vger.kernel.org> # v3.11+
Tested-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/musb/musb_virthub.c

@@ -275,9 +275,7 @@ static int musb_has_gadget(struct musb *musb)
 #ifdef CONFIG_USB_MUSB_HOST
 	return 1;
 #else
-	if (musb->port_mode == MUSB_PORT_MODE_HOST)
-		return 1;
-	return musb->g.dev.driver != NULL;
+	return musb->port_mode == MUSB_PORT_MODE_HOST;
 #endif
 }