board: sama5d4ek: 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: Andreas Bießmann <andreas@biessmann.org>
diff --git a/configs/sama5d4ek_nandflash_defconfig b/configs/sama5d4ek_nandflash_defconfig
index 3e4c0a3..a9bcabf 100644
--- a/configs/sama5d4ek_nandflash_defconfig
+++ b/configs/sama5d4ek_nandflash_defconfig
@@ -54,6 +54,12 @@
 CONFIG_SPL_PINCTRL=y
 CONFIG_PINCTRL_AT91=y
 CONFIG_DM_SERIAL=y
+CONFIG_DEBUG_UART=y
+CONFIG_DEBUG_UART_ATMEL=y
+CONFIG_DEBUG_UART_BASE=0xfc00c000
+CONFIG_DEBUG_UART_CLOCK=88000000
+CONFIG_DEBUG_UART_BOARD_INIT=y
+CONFIG_DEBUG_UART_ANNOUNCE=y
 CONFIG_ATMEL_USART=y
 CONFIG_DM_SPI=y
 CONFIG_ATMEL_SPI=y