net: dsa: rtl8366: Pass GENMASK() signed bits

Oddly, GENMASK() requires signed bit numbers, so that it can compare
them for < 0. If passed an unsigned type, we get warnings about the
test never being true.
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/rtl8366.c

@@ -272,7 +272,7 @@ int rtl8366_init_vlan(struct realtek_smi *smi)
 			/* For the CPU port, make all ports members of this
 			 * VLAN.
 			 */
-			mask = GENMASK(smi->num_ports - 1, 0);
+			mask = GENMASK((int)smi->num_ports - 1, 0);
 		else
 			/* For all other ports, enable itself plus the
 			 * CPU port.