net: dsa: b53: mmap: fix device tree support

CPU port should also be enabled in order to get a working switch.

Fixes: a5538a777b73 ("net: dsa: b53: mmap: Add device tree support")
Signed-off-by: Álvaro Fernández Rojas <[e-mail]>
Acked-by: Florian Fainelli <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/dsa/b53/b53_mmap.c

···
 		if (of_property_read_u32(of_port, "reg", &reg))
 			continue;
 
-		if (reg < B53_CPU_PORT)
+		if (reg < B53_N_PORTS)
 			pdata->enabled_ports |= BIT(reg);
 	}