embestmx6boards: Fix the dtb file name for riotboard

The name of the dtb file used in the kernel is 'imx6dl-riotboard.dtb', so fix
it accordingly.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Tested-by: Iain Paton <ipaton0@gmail.com>
diff --git a/include/configs/embestmx6boards.h b/include/configs/embestmx6boards.h
index 1d5fde6..f1000f3 100644
--- a/include/configs/embestmx6boards.h
+++ b/include/configs/embestmx6boards.h
@@ -293,7 +293,7 @@
 
 #if defined(CONFIG_ENV_IS_IN_MMC)
 /* RiOTboard */
-#define CONFIG_DEFAULT_FDT_FILE	"imx6s-riotboard.dtb"
+#define CONFIG_DEFAULT_FDT_FILE	"imx6dl-riotboard.dtb"
 #define CONFIG_SYS_FSL_USDHC_NUM	3
 #define CONFIG_SYS_MMC_ENV_DEV		2	/* SDHC4 */
 #define CONFIG_ENV_OFFSET		(6 * 64 * 1024)