staging: r8188eu: simplify rtw_alloc_xmitframe

Make the rtw_alloc_xmitframe function a bit simpler.

The container_of() call never returns NULL. The if (pxframe) check is
false only if pfree_xmit_queue is empty. Handle this special case
explicitly and save one level of indentation.
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150
Link: https://lore.kernel.org/r/20230207192319.294203-3-martin@kaiser.cxSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/r8188eu/core/rtw_xmit.c

@@ -1256,38 +1256,32 @@ struct xmit_frame *rtw_alloc_xmitframe(struct xmit_priv *pxmitpriv)/* _queue *pf
 
 	spin_lock_bh(&pfree_xmit_queue->lock);
 
-	if (list_empty(&pfree_xmit_queue->queue)) {
-		pxframe =  NULL;
-	} else {
-		phead = get_list_head(pfree_xmit_queue);
-
-		plist = phead->next;
+	if (list_empty(&pfree_xmit_queue->queue))
+		goto out;
 
-		pxframe = container_of(plist, struct xmit_frame, list);
-
-		list_del_init(&pxframe->list);
-	}
+	phead = get_list_head(pfree_xmit_queue);
+	plist = phead->next;
+	pxframe = container_of(plist, struct xmit_frame, list);
+	list_del_init(&pxframe->list);
 
-	if (pxframe) { /* default value setting */
-		pxmitpriv->free_xmitframe_cnt--;
+	pxmitpriv->free_xmitframe_cnt--;
 
-		pxframe->buf_addr = NULL;
-		pxframe->pxmitbuf = NULL;
+	pxframe->buf_addr = NULL;
+	pxframe->pxmitbuf = NULL;
 
-		memset(&pxframe->attrib, 0, sizeof(struct pkt_attrib));
-		/* pxframe->attrib.psta = NULL; */
+	memset(&pxframe->attrib, 0, sizeof(struct pkt_attrib));
+	/* pxframe->attrib.psta = NULL; */
 
-		pxframe->frame_tag = DATA_FRAMETAG;
+	pxframe->frame_tag = DATA_FRAMETAG;
 
-		pxframe->pkt = NULL;
-		pxframe->pkt_offset = 1;/* default use pkt_offset to fill tx desc */
+	pxframe->pkt = NULL;
+	pxframe->pkt_offset = 1;/* default use pkt_offset to fill tx desc */
 
-		pxframe->agg_num = 1;
-		pxframe->ack_report = 0;
-	}
+	pxframe->agg_num = 1;
+	pxframe->ack_report = 0;
 
+out:
 	spin_unlock_bh(&pfree_xmit_queue->lock);
-
 	return pxframe;
 }