powerpc:t4240rdb: Disable the non-existent ethernet ports on T4240RDB

Disable the non-existent ethernet ports on T4240RDB:FM1_DTSEC5,
FM1_DTSEC6, FM2_DTSEC5 and FM2_DTSEC6.

Signed-off-by: Ying Zhang <ying.zhang22455@nxp.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: York Sun <york.sun@nxp.com>

board/freescale/t4rdb/eth.c

@@ -77,6 +77,9 @@ int board_eth_init(bd_t *bis)
 		puts("Invalid SerDes1 protocol for T4240RDB\n");
 	}
 
+	fm_disable_port(FM1_DTSEC5);
+	fm_disable_port(FM1_DTSEC6);
+
 	for (i = FM1_DTSEC1; i < FM1_DTSEC1 + CONFIG_SYS_NUM_FM1_DTSEC; i++) {
 		interface = fm_info_get_enet_if(i);
 		switch (interface) {
@@ -115,6 +118,8 @@ int board_eth_init(bd_t *bis)
 		puts("Invalid SerDes2 protocol for T4240RDB\n");
 	}
 
+	fm_disable_port(FM2_DTSEC5);
+	fm_disable_port(FM2_DTSEC6);
 	for (i = FM2_DTSEC1; i < FM2_DTSEC1 + CONFIG_SYS_NUM_FM2_DTSEC; i++) {
 		interface = fm_info_get_enet_if(i);
 		switch (interface) {