scripts/tags.sh: Teach [ce]tags about libtraceeevent error codes

As we use a macro trick to sync each error codes with its
description string, teach [ce]tags to process them properly.

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/n/tip-qt5fv4pzigr2nnl27ydimg4h@git.kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>