usb: musb: Fix locking errors for host only mode

If we have USB gadgets disabled and USB_MUSB_HOST set, we get
errors "possible irq lock inverssion dependency detected"
errors during boot.

Let's fix the issue by adding start_musb flag and start
the controller after we're out of the spinlock protected
section.

Reported-by: Ladislav Michl <ladis@linux-mips.org>
Tested-by: Ladislav Michl <ladis@linux-mips.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/musb/musb_virthub.c

@@ -290,6 +290,7 @@ int musb_hub_control(
 	u32		temp;
 	int		retval = 0;
 	unsigned long	flags;
+	bool		start_musb = false;
 
 	spin_lock_irqsave(&musb->lock, flags);
 
@@ -390,7 +391,7 @@ int musb_hub_control(
 			 * logic relating to VBUS power-up.
 			 */
 			if (!hcd->self.is_b_host && musb_has_gadget(musb))
-				musb_start(musb);
+				start_musb = true;
 			break;
 		case USB_PORT_FEAT_RESET:
 			musb_port_reset(musb, true);
@@ -451,5 +452,9 @@ error:
 		retval = -EPIPE;
 	}
 	spin_unlock_irqrestore(&musb->lock, flags);
+
+	if (start_musb)
+		musb_start(musb);
+
 	return retval;
 }