sparc32: Fix makefile not generating required files

The tftpboot build was failing with missing file errors.

It turns out that $(obj)/image wasn't being generated which was causing the a.out conversion to be skipped and hence piggyback to be called with nonexistent files.
Signed-off-by: Julian Calaby <julian.calaby@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/boot/Makefile

@@ -58,7 +58,7 @@ $(obj)/image: $(obj)/btfix.o FORCE
 $(obj)/zImage: $(obj)/image
 	$(call if_changed,strip)
 
-$(obj)/tftpboot.img: $(obj)/piggyback_32 System.map $(ROOT_IMG) FORCE
+$(obj)/tftpboot.img: $(obj)/image $(obj)/piggyback_32 System.map $(ROOT_IMG) FORCE
 	$(call if_changed,elftoaout)
 	$(call if_changed,piggy)
 
@@ -79,7 +79,7 @@ $(obj)/image: vmlinux FORCE
 	$(call if_changed,strip)
 	@echo '  kernel: $@ is ready'
 
-$(obj)/tftpboot.img: vmlinux $(obj)/piggyback_64 System.map $(ROOT_IMG) FORCE
+$(obj)/tftpboot.img: $(obj)/image $(obj)/piggyback_64 System.map $(ROOT_IMG) FORCE
 	$(call if_changed,elftoaout)
 	$(call if_changed,piggy)
 	@echo '  kernel: $@ is ready'