rcutorture: Update rcutorture_one_extend_check() for lazy preemption

The rcutorture_one_extend_check() function's last check assumes that
if cur_ops->readlock_nesting() returns greater than zero, either the
RCUTORTURE_RDR_RCU_1 or the RCUTORTURE_RDR_RCU_2 bit must be set, that
is, there must be at least one rcu_read_lock() in effect.

This works for preemptible RCU and for non-preemptible RCU running in
a non-preemptible kernel.  But it fails for non-preemptible RCU running
in a preemptible kernel because then RCU's cur_ops->readlock_nesting()
function, which is rcu_torture_readlock_nesting(), will return
the PREEMPT_MASK mask bits from preempt_count().  The result will
be greater than zero if preemption is disabled, including by the
RCUTORTURE_RDR_PREEMPT and RCUTORTURE_RDR_SCHED bits.

This commit therefore adjusts this check to take into account the case
fo non-preemptible RCU running in a preemptible kernel.

[boqun: Fix the if condition and add comment]

Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202502171415.8ec87c87-lkp@intel.com
Co-developed-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Co-developed-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

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