ARM: imx: use #include for all device trees

Replace /include/ (dtc) with #include (C pre-processor) for all imx DT
files, so that gcc -E handles the entire include tree, and hence any of
those files can #include some other file e.g. for constant definitions.

This allows future use of #defines and header files in order to define
names for various constants, such as pinctrl settings. Use of those
features will increase the readability of the device tree files.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/boot/dts/imx53-ard.dts

@@ -11,7 +11,7 @@
  */
 
 /dts-v1/;
-/include/ "imx53.dtsi"
+#include "imx53.dtsi"
 
 / {
 	model = "Freescale i.MX53 Automotive Reference Design Board";