Tegra: fdt: Change /include/ to #include for C preprocessor

dts Makefile has the arch & board include paths added to DTS_CPPFLAGS.
This allows the use of '#include "xyz"' in the dts/dtsi file which
helps the C preprocessor find common dtsi include files.

Signed-off-by: Tom Warren <twarren@nvidia.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
diff --git a/board/nvidia/dts/tegra20-whistler.dts b/board/nvidia/dts/tegra20-whistler.dts
index 4579557..1f09e5e 100644
--- a/board/nvidia/dts/tegra20-whistler.dts
+++ b/board/nvidia/dts/tegra20-whistler.dts
@@ -1,6 +1,6 @@
 /dts-v1/;
 
-/include/ ARCH_CPU_DTS
+#include "tegra20.dtsi"
 
 / {
 	model = "NVIDIA Tegra20 Whistler evaluation board";