[PATCH] fix `make headers_install'

Fix this:

make[3]: *** No rule to make target
`/mnt/md0/devel/linux-git/include/linux/version.h', needed by
`/mnt/md0/devel/linux-git-obj/usr/include/linux/version.h'.  Stop.
make[2]: *** [linux] Error 2
make[1]: *** [headers_install] Error 2
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

scripts/Makefile.headersinst

@@ -168,7 +168,7 @@ $(objhdr-y) $(header-y) $(unifdef-y): $(KBUILDFILES)
 	$(call cmd,gen)
 
 else
-$(objhdr-y) :		$(INSTALL_HDR_PATH)/$(_dst)/%.h: $(srctree)/$(obj)/%.h $(KBUILDFILES)
+$(objhdr-y) :		$(INSTALL_HDR_PATH)/$(_dst)/%.h: $(objtree)/$(obj)/%.h $(KBUILDFILES)
 	$(call cmd,o_hdr_install)
 
 $(header-y) :		$(INSTALL_HDR_PATH)/$(_dst)/%.h: $(srctree)/$(obj)/%.h $(KBUILDFILES)