rswitch: Use unsigned int for port related array index

Array index should not be negative, so modify the condition of
rswitch_for_each_enabled_port_continue_reverse() macro, and then
use unsigned int instead.
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/renesas/rswitch.c

@@ -1405,7 +1405,8 @@ static void rswitch_ether_port_deinit_one(struct rswitch_device *rdev)
 
 static int rswitch_ether_port_init_all(struct rswitch_private *priv)
 {
-	int i, err;
+	unsigned int i;
+	int err;
 
 	rswitch_for_each_enabled_port(priv, i) {
 		err = rswitch_ether_port_init_one(priv->rdev[i]);
@@ -1786,7 +1787,8 @@ static void rswitch_device_free(struct rswitch_private *priv, int index)
 
 static int rswitch_init(struct rswitch_private *priv)
 {
-	int i, err;
+	unsigned int i;
+	int err;
 
 	for (i = 0; i < RSWITCH_NUM_PORTS; i++)
 		rswitch_etha_init(priv, i);
@@ -1816,7 +1818,7 @@ static int rswitch_init(struct rswitch_private *priv)
 	for (i = 0; i < RSWITCH_NUM_PORTS; i++) {
 		err = rswitch_device_alloc(priv, i);
 		if (err < 0) {
-			for (i--; i >= 0; i--)
+			for (; i-- > 0; )
 				rswitch_device_free(priv, i);
 			goto err_device_alloc;
 		}
@@ -1959,7 +1961,7 @@ static int renesas_eth_sw_probe(struct platform_device *pdev)
 
 static void rswitch_deinit(struct rswitch_private *priv)
 {
-	int i;
+	unsigned int i;
 
 	rswitch_gwca_hw_deinit(priv);
 	rcar_gen4_ptp_unregister(priv->ptp_priv);

drivers/net/ethernet/renesas/rswitch.h

@@ -20,7 +20,7 @@
 		else
 
 #define rswitch_for_each_enabled_port_continue_reverse(priv, i)	\
-	for (i--; i >= 0; i--)					\
+	for (; i-- > 0; )					\
 		if (priv->rdev[i]->disabled)			\
 			continue;				\
 		else