usb: musb: musbhsdma: drop the controller check in dma_controller_destroy()

This check is hardly required and alas is wrong. 'c' might be NULL but
the chances are low that 'controller' after the container_of() becomes
NULL.

Since no other DMA implementation is doing that and musb-core does not
call it with a NULL pointer it can dropped.
Signed-off-by: NSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: NFelipe Balbi <balbi@ti.com>

drivers/usb/musb/musbhsdma.c

@@ -371,9 +371,6 @@ void dma_controller_destroy(struct dma_controller *c)
 	struct musb_dma_controller *controller = container_of(c,
 			struct musb_dma_controller, controller);
 
-	if (!controller)
-		return;
-
 	if (controller->irq)
 		free_irq(controller->irq, c);