mx6sabresd: Return error if cpu_eth_init() fails

Currently board_eth_init() always return 0, but we should propagate the error
when cpu_eth_init() fails.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>

board/freescale/mx6sabresd/mx6sabresd.c

@@ -422,7 +422,7 @@ int board_eth_init(bd_t *bis)
 	if (ret)
 		printf("FEC MXC: %s:failed\n", __func__);
 
-	return 0;
+	return ret;
 }
 
 int board_early_init_f(void)