pkg/distro/deb: fix doc build for Ubuntu 18.04

Due to mysterious reasons, Ubuntu 18.04 ARM builds doesn't invoke
dh_installinfo (even though amd64 does).

Merge knot-resolver-doc.info into knot-resolver-doc.docs for
compatibility.

Author: jruzicka-nic

Diff for: distro/pkg/deb/knot-resolver-doc.docs

@@ -1 +1,3 @@
 debian/tmp/usr/share/doc/knot-resolver/html/*
+debian/tmp/usr/share/info/knot-resolver.info
+debian/tmp/usr/share/info/knot-resolver-figures/*