ARM: atmel: sama5d4ek: enable SPL support

The sama5d4ek support boot up from NAND flash, SD/MMC card and
also the SPI flash.

Signed-off-by: Bo Shen <voice.shen@atmel.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 986b4c5..8be14fe 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -529,6 +529,7 @@
 config TARGET_SAMA5D4EK
 	bool "Support sama5d4ek"
 	select CPU_V7
+	select SUPPORT_SPL
 
 config TARGET_BCM28155_AP
 	bool "Support bcm28155_ap"