Replace dts includes with C preprocessor syntax

Using the /include/ syntax, the include was evaluated by dtc, only after running
the preprocessor, therefore the .dtsi files were not preprocessed. This patch
adds the #include syntax instead. Evaluating this and preprocessing the files
now happens in a single step, done by the C preprocessor.

Change-Id: I6d0104b6274316fc736e84973502a4d6c2c9d6e0
Signed-off-by: Balint Dobszay <balint.dobszay@arm.com>
diff --git a/fdts/fvp-foundation-gicv3-psci.dts b/fdts/fvp-foundation-gicv3-psci.dts
index 1488ed7..81071e2 100644
--- a/fdts/fvp-foundation-gicv3-psci.dts
+++ b/fdts/fvp-foundation-gicv3-psci.dts
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2017, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2020, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -191,6 +191,6 @@
 			 <4 0 0 0x0c000000 0x04000000>,
 			 <5 0 0 0x10000000 0x04000000>;
 
-		/include/ "fvp-foundation-motherboard.dtsi"
+		#include "fvp-foundation-motherboard.dtsi"
 	};
 };