Move ARM device tree files to an arch-specific subfolder

FDT are also used on PPC at least, and at least skeleton.dtsi
might clash since there is a different one for PPC.

build/jam/MainBuildRules

@@ -192,7 +192,12 @@ rule CompileDTS
 
 actions CompileDTS
 {
-	cpp -P -xassembler-with-cpp -I$(HAIKU_TOP)/src/data/dts/ $(2) | dtc -O dtb -o $(1) -i $(HAIKU_TOP)/src/data/dts ;
+	cpp -P -xassembler-with-cpp \
+		-I$(HAIKU_TOP)/src/data/dts/arch/$(TARGET_ARCH) \
+		-I$(HAIKU_TOP)/src/data/dts $(2) \
+	| dtc -O dtb -o $(1) \
+		-i $(HAIKU_TOP)/src/data/dts/arch/$(TARGET_ARCH) \
+		-i $(HAIKU_TOP)/src/data/dts ;
 }
 
 rule Ld