ARM: dts: imx6: use #include "..." to include local DT

Most of DT files in ARM use #include "..." to make pre-processor
include DT in the same directory, but we have some exceptional files
that use #include <...> for that.

Fix them to remove -I$(srctree)/arch/$(SRCARCH)/boot/dts path from
dtc_cpp_flags.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6q-zii-rdu2.dts

@@ -41,8 +41,8 @@
 
 /dts-v1/;
 
-#include <imx6q.dtsi>
-#include <imx6qdl-zii-rdu2.dtsi>
+#include "imx6q.dtsi"
+#include "imx6qdl-zii-rdu2.dtsi"
 
 / {
 	model = "ZII RDU2 Board";

arch/arm/boot/dts/imx6qp-zii-rdu2.dts

@@ -41,8 +41,8 @@
 
 /dts-v1/;
 
-#include <imx6qp.dtsi>
-#include <imx6qdl-zii-rdu2.dtsi>
+#include "imx6qp.dtsi"
+#include "imx6qdl-zii-rdu2.dtsi"
 
 / {
 	model = "ZII RDU2+ Board";