hrtimer updates for RT prerequisites

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2022896
Upstream Status: Linux
Tested: Sanity tested with timer and scheduler tests

hrtimer updates for RT prerequisites

This is a series for hrtimer and related code that enable the
RT patchset to merge more cleanly.

Signed-off-by: Phil Auld pauld@redhat.com