xhci: drop null test before destroy functions

Remove unneeded NULL test.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@ expression x; @@
-if (x != NULL)
  \(kmem_cache_destroy\|mempool_destroy\|dma_pool_destroy\)(x);
// </smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-mem.c

@@ -1828,24 +1828,20 @@ void xhci_mem_cleanup(struct xhci_hcd *xhci)
 	for (i = 1; i < MAX_HC_SLOTS; ++i)
 		xhci_free_virt_device(xhci, i);
 
-	if (xhci->segment_pool)
-		dma_pool_destroy(xhci->segment_pool);
+	dma_pool_destroy(xhci->segment_pool);
 	xhci->segment_pool = NULL;
 	xhci_dbg_trace(xhci, trace_xhci_dbg_init, "Freed segment pool");
 
-	if (xhci->device_pool)
-		dma_pool_destroy(xhci->device_pool);
+	dma_pool_destroy(xhci->device_pool);
 	xhci->device_pool = NULL;
 	xhci_dbg_trace(xhci, trace_xhci_dbg_init, "Freed device context pool");
 
-	if (xhci->small_streams_pool)
-		dma_pool_destroy(xhci->small_streams_pool);
+	dma_pool_destroy(xhci->small_streams_pool);
 	xhci->small_streams_pool = NULL;
 	xhci_dbg_trace(xhci, trace_xhci_dbg_init,
 			"Freed small stream array pool");
 
-	if (xhci->medium_streams_pool)
-		dma_pool_destroy(xhci->medium_streams_pool);
+	dma_pool_destroy(xhci->medium_streams_pool);
 	xhci->medium_streams_pool = NULL;
 	xhci_dbg_trace(xhci, trace_xhci_dbg_init,
 			"Freed medium stream array pool");