dt: don't use ARCH_CPU_DTS

Now that we assume dtc supports the -i option, we don't need to use
ARCH_CPU_DTS in *.dts{,i}; we simply specify the include filename
directly, and dtc will find it.
Signed-off-by: NStephen Warren <swarren@nvidia.com>
Acked-by: NSimon Glass <sjg@chromium.org>

board/chromebook-x86/dts/link.dts

 /dts-v1/;
 
-/include/ ARCH_CPU_DTS
+/include/ "coreboot.dtsi"
 
 / {
         #address-cells = <1>;

board/samsung/dts/exynos5250-smdk5250.dts

@@ -10,7 +10,7 @@
 */
 
 /dts-v1/;
-/include/ ARCH_CPU_DTS
+/include/ "exynos5250.dtsi"
 
 / {
 	model = "SAMSUNG SMDK5250 board based on EXYNOS5250";

board/samsung/dts/exynos5250-snow.dts

@@ -10,7 +10,7 @@
 */
 
 /dts-v1/;
-/include/ ARCH_CPU_DTS
+/include/ "exynos5250.dtsi"
 
 / {
 	model = "Google Snow";