embestmx6boards: Add SPL support

In order to boot faster with falcon mode, we need to add SPL
support to riotboard.

Signed-off-by: Fabien Lahoudere <fabien.lahoudere@collabora.com>
diff --git a/arch/arm/mach-imx/mx6/Kconfig b/arch/arm/mach-imx/mx6/Kconfig
index 06c25ba..e7cce46 100644
--- a/arch/arm/mach-imx/mx6/Kconfig
+++ b/arch/arm/mach-imx/mx6/Kconfig
@@ -182,6 +182,7 @@
 config TARGET_EMBESTMX6BOARDS
 	bool "embestmx6boards"
 	select BOARD_LATE_INIT
+	select SUPPORT_SPL
 
 config TARGET_GE_BX50V3
 	bool "General Electric Bx50v3"