About 40% of all csd_lock warnings observed in our fleet appear to
be due to sched_clock() going backward in time (usually only a little
bit), resulting in ts0 being larger than ts2.

When the local CPU is at fault, we should print out a message reflecting
that, rather than trying to get the remote CPU's stack trace.
Signed-off-by: Rik van Riel <riel@surriel.com>
Tested-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>