net: sparx5: fix resource_size.cocci warnings

Use resource_size function on resource object
instead of explicit computation.

Clean up coccicheck warning:
./drivers/net/ethernet/microchip/sparx5/sparx5_main.c:237:19-22: ERROR:
Missing resource_size with iores [ idx ]
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/microchip/sparx5/sparx5_main.c

@@ -234,8 +234,7 @@ static int sparx5_create_targets(struct sparx5 *sparx5)
 		}
 		iomem[idx] = devm_ioremap(sparx5->dev,
 					  iores[idx]->start,
-					  iores[idx]->end - iores[idx]->start
-					  + 1);
+					  resource_size(iores[idx]));
 		if (!iomem[idx]) {
 			dev_err(sparx5->dev, "Unable to get switch registers: %s\n",
 				iores[idx]->name);