rtl83xx: fix STP by trapping BPDUs

Fix Spanning Tree Protocol (STP) by changing COPY2CPU which currently
makes switch to ignore Bridge Protocol Data Units (BPDUs).

Tested on Zyxel GS1900-8, 24 and 48.

Signed-off-by: Rudolf Vesely <[email protected]>
[ improve commit description and add new line in different sections ]
Signed-off-by: Christian Marangi <[email protected]>

target/linux/realtek/files-5.15/drivers/net/dsa/rtl83xx/dsa.c

@@ -152,7 +152,7 @@ static void rtl83xx_vlan_setup(struct rtl838x_switch_priv *priv)
 static void rtl83xx_setup_bpdu_traps(struct rtl838x_switch_priv *priv)
 {
 	for (int i = 0; i < priv->cpu_port; i++)
-		priv->r->set_receive_management_action(i, BPDU, COPY2CPU);
+		priv->r->set_receive_management_action(i, BPDU, TRAP2CPU);
 }
 
 static void rtl83xx_port_set_salrn(struct rtl838x_switch_priv *priv,