net: dsa: realtek: rtl8365mb: use GENMASK(n-1,0) instead of BIT(n)-1

Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
Tested-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/realtek/rtl8365mb.c

@@ -1968,7 +1968,7 @@ static int rtl8365mb_detect(struct realtek_priv *priv)
 		mb->priv = priv;
 		mb->chip_id = chip_id;
 		mb->chip_ver = chip_ver;
-		mb->port_mask = BIT(priv->num_ports) - 1;
+		mb->port_mask = GENMASK(priv->num_ports - 1, 0);
 		mb->learn_limit_max = RTL8365MB_LEARN_LIMIT_MAX_8365MB_VC;
 		mb->jam_table = rtl8365mb_init_jam_8365mb_vc;
 		mb->jam_size = ARRAY_SIZE(rtl8365mb_init_jam_8365mb_vc);