net: airoha: avoid out of boundary writing/access to gdm_port_str[] array

In the case of an7581 possible GDM port id are: 1, 2 and 4.
Initialization of port GDM4 will lead to out of boundary writing
to gdm_port_str[] array.

Let's increase the array size by 1 to avoid it.

Signed-off-by: Mikhail Kshevetskiy <mikhail.kshevetskiy@iopsys.eu>

drivers/net/airoha_eth.c

@@ -331,7 +331,7 @@ struct airoha_eth {
 	struct airoha_eth_soc_data *soc;
 
 	struct airoha_qdma qdma[AIROHA_MAX_NUM_QDMA];
-	char gdm_port_str[AIROHA_MAX_NUM_GDM_PORTS][AIROHA_GDM_PORT_STRING_LEN];
+	char gdm_port_str[AIROHA_MAX_NUM_GDM_PORTS + 1][AIROHA_GDM_PORT_STRING_LEN];
 };
 
 struct airoha_eth_soc_data {