usb: otg: prefix otg_state_string with usb_

all other functions under drivers/usb/ start
with usb_, let's do the same thing.

This patch is in preparation for moving otg_state_string
to usb-common.c and deleting otg.c completely.

Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/musb/musb_host.c

@@ -2453,7 +2453,7 @@ static int musb_bus_suspend(struct usb_hcd *hcd)
 
 	if (musb->is_active) {
 		WARNING("trying to suspend as %s while active\n",
-				otg_state_string(musb->xceiv->state));
+				usb_otg_state_string(musb->xceiv->state));
 		return -EBUSY;
 	} else
 		return 0;