tools/xenalyze: Get rid of extraneous data structure

tools/xenalyze: Get rid of extraneous data structure

The only difference between event_cycle_summary and cycle_summary was
that the former has a separate counter for "events" which had
zero-cycle events.  But a lot of the code dealing with them had to be
duplicated with slightly different fields.

Remove event_cycle_summary, add an "event_count" field to
cycle_symmary, and use cycle_summary for everything.

Signed-off-by: George Dunlap <george.dunlap@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>