ARM: atmel: at91sam9n12ek: enable spl support

Enable SPL support for at91sam9n12ek boards, now it supports
boot up from NAND flash, serial flash.

Signed-off-by: Bo Shen <voice.shen@atmel.com>
diff --git a/arch/arm/mach-at91/Kconfig b/arch/arm/mach-at91/Kconfig
index bdf87f9..30c4e17 100644
--- a/arch/arm/mach-at91/Kconfig
+++ b/arch/arm/mach-at91/Kconfig
@@ -75,6 +75,7 @@
 config TARGET_AT91SAM9N12EK
 	bool "Atmel AT91SAM9N12-EK board"
 	select CPU_ARM926EJS
+	select SUPPORT_SPL
 
 config TARGET_AT91SAM9RLEK
 	bool "Atmel at91sam9rl reference board"