whci: 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/whci/init.c

@@ -175,8 +175,7 @@ void whc_clean_up(struct whc *whc)
 	pzl_clean_up(whc);
 	asl_clean_up(whc);
 
-	if (whc->qset_pool)
-		dma_pool_destroy(whc->qset_pool);
+	dma_pool_destroy(whc->qset_pool);
 
 	len   = resource_size(&whc->umc->resource);
 	if (whc->base)