arc: Use full path in KBUILD_IMAGE definition

The KBUILD_IMAGE variable is used by the rpm and deb-pkg targets, which
expect it to point to the image file in the build directory. The
builddeb script has a workaround for architectures which only provide
the basename, but let's provide a clean interface for packaging tools.

Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: linux-snps-arc@lists.infradead.org
Signed-off-by: Michal Marek <mmarek@suse.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

arch/arc/Makefile

@@ -123,9 +123,9 @@ libs-y		+= arch/arc/lib/ $(LIBGCC)
 boot		:= arch/arc/boot
 
 #default target for make without any arguments.
-KBUILD_IMAGE	:= bootpImage
+KBUILD_IMAGE	:= $(boot)/bootpImage
 
-all:	$(KBUILD_IMAGE)
+all:	bootpImage
 bootpImage: vmlinux
 
 boot_targets += uImage uImage.bin uImage.gz