Fix following warnings:

  event-parse.c: In function ‘tep_find_event_by_name’:
  event-parse.c:3521:21: warning: ‘event’ may be used uninitialized in this function [-Wmaybe-uninitialized]
    pevent->last_event = event;
    ~~~~~~~~~~~~~~~~~~~^~~~~~~
    CC       ui/gtk/hists.o
    LINK     plugin_mac80211.so
    CC       nlattr.o
  event-parse.c: In function ‘tep_data_lat_fmt’:
  event-parse.c:5200:4: warning: ‘migrate_disable’ may be used uninitialized in this function [-Wmaybe-uninitialized]
      trace_seq_printf(s, "%d", migrate_disable);
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  event-parse.c:5207:4: warning: ‘lock_depth’ may be used uninitialized in this function [-Wmaybe-uninitialized]
      trace_seq_printf(s, "%d", lock_depth);
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    LINK     plugin_sched_switch.so
    LINK     plugin_function.so
    LINK     plugin_xen.so
  event-parse.c: In function ‘tep_event_info’:
  event-parse.c:5047:7: warning: ‘len_arg’ may be used uninitialized in this function [-Wmaybe-uninitialized]
         trace_seq_printf(s, format, len_arg, (char)val);
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  event-parse.c:4884:6: note: ‘len_arg’ was declared here
    int len_arg;
        ^~~~~~~
  event-parse.c:4338:11: warning: ‘vsize’ may be used uninitialized in this function [-Wmaybe-uninitialized]
       val = tep_read_number(pevent, bptr, vsize);
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  event-parse.c:4224:6: note: ‘vsize’ was declared here
    int vsize;
        ^~~~~

$ gcc --version
  gcc (Clear Linux OS for Intel Architecture) 8.2.1 20180502
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
Link: http://lkml.kernel.org/r/20181122112937.10582-1-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>