dynamic_debug: tighten up error checking on debug queries

Issue error when a match-spec is given multiple times in a rule.
Previous code kept last one, but was silent about it.  Docs imply only
one is allowed by saying match-specs are ANDed together, given that
module M cannot match both A and B.  Also error when last_line < 1st_line.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>