USB: gadget: Drop NULL test on list_entry result

list_entry, which is an alias for container_of, cannot return NULL, as
there is no way to add a NULL value to a doubly linked list.

A simplified version of the semantic match that findds this problem is as
follows:
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@r@
expression x,E;
statement S1,S2;
position p,p1;
@@

*x = list_entry@p(...)
... when != x = E
*if@p1 (x == NULL) S1 else S2
// </smpl>
Signed-off-by: NJulia Lawall <julia@diku.dk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/usb/gadget/amd5536udc.c

@@ -2378,7 +2378,6 @@ static irqreturn_t udc_data_in_isr(struct udc *dev, int ep_ix)
 		if (!ep->cancel_transfer && !list_empty(&ep->queue)) {
 			req = list_entry(ep->queue.next,
 					struct udc_request, queue);
-			if (req) {
 			/*
 			 * length bytes transfered
 			 * check dma done of last desc. in PPBDU mode
@@ -2390,8 +2389,7 @@ static irqreturn_t udc_data_in_isr(struct udc *dev, int ep_ix)
 						AMD_GETBITS(td->status,
 						UDC_DMA_IN_STS_BS);
 					/* don't care DMA done */
-						req->req.actual =
-							req->req.length;
+					req->req.actual = req->req.length;
 				}
 			} else {
 				/* assume all bytes transferred */
@@ -2405,13 +2403,9 @@ static irqreturn_t udc_data_in_isr(struct udc *dev, int ep_ix)
 				/* further request available ? */
 				if (list_empty(&ep->queue)) {
 					/* disable interrupt */
-						tmp = readl(
-							&dev->regs->ep_irqmsk);
+					tmp = readl(&dev->regs->ep_irqmsk);
 					tmp |= AMD_BIT(ep->num);
-						writel(tmp,
-							&dev->regs->ep_irqmsk);
-					}
-
+					writel(tmp, &dev->regs->ep_irqmsk);
 				}
 			}
 		}