rcutorture: Generic test for NUM_ACTIVE_*RCU_POLL*

rcutorture: Generic test for NUM_ACTIVE_*RCU_POLL*

The rcutorture test suite has specific tests for both of the
NUM_ACTIVE_RCU_POLL_OLDSTATE and NUM_ACTIVE_RCU_POLL_FULL_OLDSTATE
macros provided for RCU polled grace periods.  However, with the
advent of NUM_ACTIVE_SRCU_POLL_OLDSTATE, a more generic test is needed.
This commit therefore adds ->poll_active and ->poll_active_full fields
to the rcu_torture_ops structure and converts the existing specific
tests to use these fields, when present.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>