mx51evk: do not overwrite the console

On this board, the console is always set to the serial line.
Do not allow to overwrite it when video is enabled.

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

board/freescale/mx51evk/mx51evk.c

@@ -536,12 +536,20 @@ int board_late_init(void)
 	setup_iomux_spi();
 	power_init();
 #endif
-	setenv("stdout", "serial");
 
 	return 0;
 }
 #endif
 
+/*
+ * Do not overwrite the console
+ * Use always serial for U-Boot console
+ */
+int overwrite_console(void)
+{
+	return 1;
+}
+
 int checkboard(void)
 {
 	puts("Board: MX51EVK\n");

include/configs/mx51evk.h

@@ -128,6 +128,8 @@
 #define CONFIG_VIDEO_IPUV3
 #define CONFIG_CFB_CONSOLE
 #define CONFIG_VGA_AS_SINGLE_DEVICE
+#define CONFIG_SYS_CONSOLE_IS_IN_ENV
+#define CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
 #define CONFIG_VIDEO_BMP_RLE8
 #define CONFIG_SPLASH_SCREEN
 #define CONFIG_BMP_16BPP