csky: remove builtin-dtb Kbuild

Remove the builtin-dtb implementation in arch/csky.
Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>

arch/csky/Kconfig.debug

-menu "C-SKY Debug Options"
-config CSKY_BUILTIN_DTB
-	string "Use kernel builtin dtb"
-	help
-	  User could define the dtb instead of the one which is passed from
-	  bootloader.
-	  Sometimes for debug, we want to use a built-in dtb and then we needn't
-	  modify bootloader at all.
-endmenu
+# dummy file, do not delete

arch/csky/Makefile

@@ -65,9 +65,7 @@ libs-y += arch/csky/lib/ \
 	$(shell $(CC) $(KBUILD_CFLAGS) $(KCFLAGS) -print-libgcc-file-name)
 
 boot := arch/csky/boot
-ifneq '$(CONFIG_CSKY_BUILTIN_DTB)' '""'
 core-y += $(boot)/dts/
-endif
 
 all: zImage
 

arch/csky/boot/dts/Makefile

 dtstree	:= $(srctree)/$(src)
 
-ifneq '$(CONFIG_CSKY_BUILTIN_DTB)' '""'
-builtindtb-y := $(patsubst "%",%,$(CONFIG_CSKY_BUILTIN_DTB))
-dtb-y += $(builtindtb-y).dtb
-obj-y += $(builtindtb-y).dtb.o
-.SECONDARY: $(obj)/$(builtindtb-y).dtb.S
-else
 dtb-y := $(patsubst $(dtstree)/%.dts,%.dtb, $(wildcard $(dtstree)/*.dts))
-endif
 
 always += $(dtb-y)
 clean-files += *.dtb *.dtb.S