ARM: dt: change .dtb build rules to build in dts directory

The current rules have the .dtb files build in a different directory
from the .dts files. The only reason for this is that it was what
PowerPC has done historically. This patch changes ARM to use the generic
dtb rule which builds .dtb files in the same directory as the source .dts.

Cc: Russell King <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Acked-by: Olof Johansson <[e-mail]>
Cc: [e-mail]
Signed-off-by: Grant Likely <[e-mail]>
[swarren: added rm command for old stale .dtb files]
Signed-off-by: Stephen Warren <[e-mail]>
Signed-off-by: Rob Herring <[e-mail]>

arch/arm/Makefile

···
 	$(Q)$(MAKE) $(build)=$(boot) MACHINE=$(MACHINE) $@
 
 %.dtb: scripts
-	$(Q)$(MAKE) $(build)=$(boot) MACHINE=$(MACHINE) $(boot)/$@
+	$(Q)$(MAKE) $(build)=$(boot)/dts MACHINE=$(MACHINE) $(boot)/dts/$@
 
 dtbs: scripts
-	$(Q)$(MAKE) $(build)=$(boot) MACHINE=$(MACHINE) $(boot)/$@
+	$(Q)$(MAKE) $(build)=$(boot)/dts MACHINE=$(MACHINE) dtbs
 
 # We use MRPROPER_FILES and CLEAN_FILES now
 archclean:

arch/arm/boot/Makefile

···
 include $(srctree)/$(MACHINE)/Makefile.boot
 endif
 
-include $(srctree)/arch/arm/boot/dts/Makefile
-
 # Note: the following conditions must always be true:
 #   ZRELADDR == virt_to_phys(PAGE_OFFSET + TEXT_OFFSET)
 #   PARAMS_PHYS must be within 4MB of ZRELADDR
···
 	$(kecho) '  Kernel: $@ is ready'
 
 endif
-
-targets += $(dtb-y)
-
-# Rule to build device tree blobs
-$(obj)/%.dtb: $(src)/dts/%.dts FORCE
-	$(call if_changed_dep,dtc)
-
-$(obj)/dtbs: $(addprefix $(obj)/, $(dtb-y))
-
-clean-files := *.dtb
 
 ifneq ($(LOADADDR),)
   UIMAGE_LOADADDR=$(LOADADDR)

arch/arm/boot/dts/Makefile

···
 	wm8505-ref.dtb \
 	wm8650-mid.dtb
 
+targets += dtbs
 endif
+
+# *.dtb used to be generated in the directory above. Clean out the
+# old build results so people don't accidentally use them.
+dtbs: $(addprefix $(obj)/, $(dtb-y))
+	$(Q)rm -f $(obj)/../*.dtb
+
+clean-files := *.dtb