kbuild: refactor Makefile.dtbinst more

Refactor Makefile.dtbinst so it looks similar to other Makefiles.

*.dtb should not be a phony target. Copy files based on the timestamps.
Print installed dtb paths instead of in-kernel dtb paths.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/Makefile.dtbinst

@@ -17,20 +17,20 @@ include include/config/auto.conf
 include scripts/Kbuild.include
 include $(src)/Makefile
 
-dtbinst-files	:= $(sort $(dtb-y) $(if $(CONFIG_OF_ALL_DTBS), $(dtb-)))
-dtbinst-dirs	:= $(subdir-y) $(subdir-m)
+dtbs    := $(addprefix $(dst)/, $(dtb-y) $(if $(CONFIG_OF_ALL_DTBS),$(dtb-)))
+subdirs := $(addprefix $(obj)/, $(subdir-y) $(subdir-m))
 
-# Helper targets for Installing DTBs into the boot directory
-quiet_cmd_dtb_install =	INSTALL $<
-      cmd_dtb_install =	mkdir -p $(2); cp $< $(2)
+__dtbs_install: $(dtbs) $(subdirs)
+	@:
 
-$(dtbinst-files): %.dtb: $(obj)/%.dtb
-	$(call cmd,dtb_install,$(dst))
+quiet_cmd_dtb_install = INSTALL $@
+      cmd_dtb_install = install -D $< $@
 
-$(dtbinst-dirs):
-	$(Q)$(MAKE) $(dtbinst)=$(obj)/$@ dst=$(dst)/$@
+$(dst)/%.dtb: $(obj)/%.dtb
+	$(call cmd,dtb_install)
 
-PHONY += $(dtbinst-files) $(dtbinst-dirs)
-__dtbs_install: $(dtbinst-files) $(dtbinst-dirs)
+PHONY += $(subdirs)
+$(subdirs):
+	$(Q)$(MAKE) $(dtbinst)=$@ dst=$(patsubst $(obj)/%,$(dst)/%,$@)
 
 .PHONY: $(PHONY)