This commit annotates rcu_initiate_boost() fixes the following sparse
warning:
kernel/rcu/tree_plugin.h:1494:13: warning: context imbalance in 'rcu_initiate_boost' - unexpected unlock
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>