rcu: Clean up flavor-related definitions and comments in rcupdate_wait.h

/**

 * synchronize_rcu_mult - Wait concurrently for multiple grace periods

 * @...: List of call_rcu() functions for the flavors to wait on.

 * @...: List of call_rcu() functions for different grace periods to wait on

 *

 * This macro waits concurrently for multiple flavors of RCU grace periods.

 * For example, synchronize_rcu_mult(call_rcu, call_rcu_sched) would wait

 * on concurrent RCU and RCU-sched grace periods.  Waiting on a give SRCU

 * This macro waits concurrently for multiple types of RCU grace periods.

 * For example, synchronize_rcu_mult(call_rcu, call_rcu_tasks) would wait

 * on concurrent RCU and RCU-tasks grace periods.  Waiting on a give SRCU

 * domain requires you to write a wrapper function for that SRCU domain's

 * call_srcu() function, supplying the corresponding srcu_struct.

 *

 * If Tiny RCU, tell _wait_rcu_gp() not to bother waiting for RCU

 * or RCU-sched, given that anywhere synchronize_rcu_mult() can be called

 * is automatically a grace period.

 * If Tiny RCU, tell _wait_rcu_gp() does not bother waiting for RCU,

 * given that anywhere synchronize_rcu_mult() can be called is automatically

 * a grace period.

 */

#define synchronize_rcu_mult(...) \

	_wait_rcu_gp(IS_ENABLED(CONFIG_TINY_RCU), __VA_ARGS__)