ARM: keystone: use #include to include skeleton.dtsi

Replace /include/ (dtc) with #include (C pre-processor) to
include skeleton.dtsi
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>

arch/arm/boot/dts/keystone.dts

@@ -7,7 +7,7 @@
  */
 
 /dts-v1/;
-/include/ "skeleton.dtsi"
+#include "skeleton.dtsi"
 
 / {
 	model = "Texas Instruments Keystone 2 SoC";