patch 8.1.0623: iterating through window frames is repeated

Problem:    Iterating through window frames is repeated.
Solution:   Define FOR_ALL_FRAMES. (Yegappan Lakshmanan)
diff --git a/src/screen.c b/src/screen.c
index 4a61807..ed1d4a3 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -6681,7 +6681,7 @@
 	frp->fr_win->w_redr_status = TRUE;
     else if (frp->fr_layout == FR_ROW)
     {
-	for (frp = frp->fr_child; frp != NULL; frp = frp->fr_next)
+	FOR_ALL_FRAMES(frp, frp->fr_child)
 	    win_redraw_last_status(frp);
     }
     else /* frp->fr_layout == FR_COL */