c6x: use common built-in dtb support

Using the common build support for built-in dtb files just requires
adding a .dtb.o target to obj-y.

The dtb now needs to be copied when unflattened because an init section
is used now.

Cc: Mark Salter <msalter@redhat.com>
Cc: Aurelien Jacquiot <jacquiot.aurelien@gmail.com>
Cc: linux-c6x-dev@linux-c6x.org
Signed-off-by: Rob Herring <robh@kernel.org>

arch/c6x/boot/dts/Makefile

@@ -6,14 +6,5 @@
 DTC_FLAGS ?= -p 1024
 
 ifneq ($(DTB),)
-obj-y += linked_dtb.o
+obj-y += $(DTB).dtb.o
 endif
-
-quiet_cmd_cp = CP      $< $@$2
-	cmd_cp = cat $< >$@$2 || (rm -f $@ && echo false)
-
-# Generate builtin.dtb from $(DTB).dtb
-$(obj)/builtin.dtb: $(obj)/$(DTB).dtb
-	$(call if_changed,cp)
-
-$(obj)/linked_dtb.o: $(obj)/builtin.dtb

arch/c6x/boot/dts/linked_dtb.S

@@ -1,2 +0,0 @@
-.section __fdt_blob,"a"
-.incbin "arch/c6x/boot/dts/builtin.dtb"