makefile: fixed release target

Added MAINTAINERS, doc and README.markdown to the tar archive
generation logic.

Signed-off-by: Clark Williams <williams@redhat.com>
diff --git a/Makefile b/Makefile
index c663a54..a48e759 100644
--- a/Makefile
+++ b/Makefile
@@ -157,7 +157,7 @@
 release: distclean changelog
 	mkdir -p releases
 	mkdir -p tmp/rt-tests
-	cp -r Makefile COPYING ChangeLog src tmp/rt-tests
+	cp -r Makefile COPYING ChangeLog MAINTAINERS doc README.markdown src tmp/rt-tests
 	rm -f rt-tests-$(VERSION_STRING).tar rt-tests-$(VERSION_STRING).tar.asc
 	tar -C tmp -cf rt-tests-$(VERSION_STRING).tar rt-tests
 	gpg2 --default-key clrkwllms@kernel.org --detach-sign --armor rt-tests-$(VERSION_STRING).tar