rcu: Clean up flavor-related definitions and comments in Kconfig

	  This option boosts the priority of preempted RCU readers that

	  block the current preemptible RCU grace period for too long.

	  This option also prevents heavy loads from blocking RCU

	  callback invocation for all flavors of RCU.

	  callback invocation.

	  Say Y here if you are working with real-time apps or heavy loads

	  Say N here if you are unsure.

	  callback invocation to energy-efficient CPUs in battery-powered

	  asymmetric multiprocessors.

	  This option offloads callback invocation from the set of

	  CPUs specified at boot time by the rcu_nocbs parameter.

	  For each such CPU, a kthread ("rcuox/N") will be created to

	  invoke callbacks, where the "N" is the CPU being offloaded,

	  and where the "p" for RCU-preempt and "s" for RCU-sched.

	  Nothing prevents this kthread from running on the specified

	  CPUs, but (1) the kthreads may be preempted between each

	  callback, and (2) affinity or cgroups can be used to force

	  the kthreads to run on whatever set of CPUs is desired.

	  This option offloads callback invocation from the set of CPUs

	  specified at boot time by the rcu_nocbs parameter.  For each

	  such CPU, a kthread ("rcuox/N") will be created to invoke

	  callbacks, where the "N" is the CPU being offloaded, and where

	  the "p" for RCU-preempt (PREEMPT kernels) and "s" for RCU-sched

	  (!PREEMPT kernels).  Nothing prevents this kthread from running

	  on the specified CPUs, but (1) the kthreads may be preempted

	  between each callback, and (2) affinity or cgroups can be used

	  to force the kthreads to run on whatever set of CPUs is desired.

	  Say Y here if you want to help to debug reduced OS jitter.

	  Say N here if you are unsure.