net: dsa: dsa_fastest_ageing_time return unsigned

The ageing time is defined as unsigned int, so make
dsa_fastest_ageing_time return an unsigned int instead of int.
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/slave.c

@@ -419,7 +419,7 @@ static int dsa_slave_vlan_filtering(struct net_device *dev,
 	return 0;
 }
 
-static int dsa_fastest_ageing_time(struct dsa_switch *ds,
+static unsigned int dsa_fastest_ageing_time(struct dsa_switch *ds,
 					    unsigned int ageing_time)
 {
 	int i;