torture: Make torture_hrtimeout_ns() take an hrtimer mode parameter

[ Upstream commit a741deac787f0d2d7068638c067db20af9e63752 ]

The current torture-test sleeps are waiting for a duration, but there
are situations where it is better to wait for an absolute time, for
example, when ending a stutter interval.  This commit therefore adds
an hrtimer mode parameter to torture_hrtimeout_ns().  Why not also the
other torture_hrtimeout_*() functions?  The theory is that most absolute
times will be in nanoseconds, especially not (say) jiffies.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Stable-dep-of: cca42bd8eb1b ("rcutorture: Fix stuttering races and other issues")
Signed-off-by: Sasha Levin <sashal@kernel.org>