perf sched timehist: Handle cpu migration events

Add handlers for sched:sched_migrate_task event. Total number of
migrations is added to summary display and -M/--migrations can be used
to show migration events.

Signed-off-by: David Ahern <dsahern@gmail.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/1480091321-35591-1-git-send-email-dsa@cumulusnetworks.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>