staging: r8188eu: use list_empty

Use list_empty to check for an empty list instead of coding the check
manually.
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/20230123205342.229589-11-martin@kaiser.cxSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/r8188eu/core/rtw_xmit.c

@@ -1363,7 +1363,7 @@ static struct xmit_frame *dequeue_one_xmitframe(struct tx_servq *ptxservq, struc
 	xmitframe_phead = get_list_head(pframe_queue);
 	xmitframe_plist = xmitframe_phead->next;
 
-	if (xmitframe_phead != xmitframe_plist) {
+	if (!list_empty(xmitframe_phead)) {
 		pxmitframe = container_of(xmitframe_plist, struct xmit_frame, list);
 		list_del_init(&pxmitframe->list);
 		ptxservq->qcnt--;