tools lib traceevent: Fix format in plugin_kvm

The format field argument passed to the format
in pevent_print_num_field() will be of type long long. That means that
%ll must be used instead of %l.

Acked-by: Namhyung Kim <namhyung@kernel.org>
Reported-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20140613103127.1a9bdee7@gandalf.local.home
Signed-off-by: Jiri Olsa <jolsa@kernel.org>