imx: mx6slevk: introduce device tree support

Introduce device tree support.
dts from kernel commit c4f3f22edd Merge tag 'linux-kselftest-4.11-rc1'

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
index afeb43f..aa0bd12 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -311,6 +311,7 @@
 dtb-$(CONFIG_MX53) += imx53-cx9020.dtb
 
 dtb-$(CONFIG_MX6) += imx6ull-14x14-evk.dtb \
+	imx6sl-evk.dtb \
 	imx6sll-evk.dtb \
 	imx6dl-icore.dtb \
 	imx6dl-icore-rqs.dtb \