kbuild: simplify the %_shipped rule

This is needed to have make(1) correctly link the implicit rules which
generate the _shipped file from the lexer/parser to the final file.
Signed-off-by: NArnaud Lacombe <lacombar@gmail.com>

scripts/Makefile.lib

@@ -204,7 +204,7 @@ endif
 quiet_cmd_shipped = SHIPPED $@
 cmd_shipped = cat $< > $@
 
-$(obj)/%:: $(src)/%_shipped
+$(obj)/%: $(src)/%_shipped
 	$(call cmd,shipped)
 
 # Commands useful for building a boot image