rcu: Remove rsp parameter from CPU hotplug functions

There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_cleanup_dying_cpu() and rcu_cleanup_dead_cpu().  And, as long as
we are in the neighborhood, inlines them into rcutree_dying_cpu() and
rcutree_dead_cpu(), respectively.  This also eliminates a pair of
for_each_rcu_flavor() loops.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>