board: at91sam9n12ek: Enable early debug UART

Enable the early debug UART to debug problems when an ICE or other
debug mechanism is not available.

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/board/atmel/at91sam9n12ek/at91sam9n12ek.c b/board/atmel/at91sam9n12ek/at91sam9n12ek.c
index 02b7790..1105428 100644
--- a/board/atmel/at91sam9n12ek/at91sam9n12ek.c
+++ b/board/atmel/at91sam9n12ek/at91sam9n12ek.c
@@ -13,6 +13,7 @@
 #include <asm/arch/at91_rstc.h>
 #include <asm/arch/at91_pio.h>
 #include <asm/arch/clk.h>
+#include <debug_uart.h>
 #include <lcd.h>
 #include <atmel_hlcdc.h>
 #include <netdev.h>
@@ -162,10 +163,22 @@
 }
 #endif
 
+#ifdef CONFIG_DEBUG_UART_BOARD_INIT
+void board_debug_uart_init(void)
+{
+	at91_seriald_hw_init();
+}
+#endif
+
+#ifdef CONFIG_BOARD_EARLY_INIT_F
 int board_early_init_f(void)
 {
+#ifdef CONFIG_DEBUG_UART
+	debug_uart_init();
+#endif
 	return 0;
 }
+#endif
 
 int board_init(void)
 {