USB-EHCI: Delete unnecessary checks before the function call "dma_pool_destroy"

The dma_pool_destroy() function tests whether its argument is NULL
and then returns immediately. Thus the test around the calls is not needed.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <[e-mail]>
Acked-by: Alan Stern <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/host/ehci-mem.c

···
 	ehci->dummy = NULL;
 
 	/* DMA consistent memory and pools */
-	if (ehci->qtd_pool)
-		dma_pool_destroy (ehci->qtd_pool);
+	dma_pool_destroy(ehci->qtd_pool);
 	ehci->qtd_pool = NULL;
-
-	if (ehci->qh_pool) {
-		dma_pool_destroy (ehci->qh_pool);
-		ehci->qh_pool = NULL;
-	}
-
-	if (ehci->itd_pool)
-		dma_pool_destroy (ehci->itd_pool);
+	dma_pool_destroy(ehci->qh_pool);
+	ehci->qh_pool = NULL;
+	dma_pool_destroy(ehci->itd_pool);
 	ehci->itd_pool = NULL;
-
-	if (ehci->sitd_pool)
-		dma_pool_destroy (ehci->sitd_pool);
+	dma_pool_destroy(ehci->sitd_pool);
 	ehci->sitd_pool = NULL;
 
 	if (ehci->periodic)