rcu: Remove rsp parameter from rcu_print_detail_task_stall()

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_print_detail_task_stall().

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