package: Makefile: unbreak binrpm-pkg target

Commit 65013203 dropped the rpm spec as a
prerequisite for the binrpm-pkg target but forgot to update $< usage,
which causes the rule to break.

This commit fixes that by replacing $< with the spec name.
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>

scripts/package/Makefile

@@ -63,7 +63,7 @@ binrpm-pkg: FORCE
 	mv -f $(objtree)/.tmp_version $(objtree)/.version
 
 	$(RPM) $(RPMOPTS) --define "_builddir $(objtree)" --target \
-		$(UTS_MACHINE) -bb $<
+		$(UTS_MACHINE) -bb $(objtree)/binkernel.spec
 	rm binkernel.spec
 
 # Deb target