scripts/dtc: dtx_diff - update include dts paths to match build

commit b4b201d8 upstream.

Update the cpp include flags for compiling device tree dts files
to match the changes made to the kernel build process in
commit d5d332d3 ("devicetree: Move include prefixes from arch
to separate directory").
Signed-off-by: Frank Rowand <frank.rowand@sony.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

scripts/dtc/dtx_diff

@@ -321,7 +321,7 @@ fi
 cpp_flags="\
 	-nostdinc                                  \
 	-I${srctree}/arch/${ARCH}/boot/dts         \
-	-I${srctree}/arch/${ARCH}/boot/dts/include \
+	-I${srctree}/scripts/dtc/include-prefixes  \
 	-I${srctree}/drivers/of/testcase-data      \
 	-undef -D__DTS__"