ARM: socfpga: dts: convert to preprocessor includes

Convert all socfpga DT files to the dtc preprocessor include syntax.
This allows to include header files in the devicetrees like other
SoC-types already do.

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Dinh Nguyen <dinguyen@altera.com>

arch/arm/boot/dts/socfpga.dtsi

@@ -15,7 +15,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-/include/ "skeleton.dtsi"
+#include "skeleton.dtsi"
 
 / {
 	#address-cells = <1>;