octeontx2-af: use swap() to make code cleaner

Use the macro 'swap()' defined in 'include/linux/minmax.h' to avoid
opencoding it.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Yang Guang <yang.guang5@zte.com.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/octeontx2/af/rvu_npc.c

@@ -2450,9 +2450,7 @@ alloc:
 		bmap = mcam->bmap_reverse;
 		start = mcam->bmap_entries - start;
 		end = mcam->bmap_entries - end;
-		index = start;
-		start = end;
-		end = index;
+		swap(start, end);
 	} else {
 		bmap = mcam->bmap;
 	}