The current (and implicit) comment header for init_rcu_head() and
destroy_rcu_head() incorrectly says that they are not needed for
statically allocated rcu_head structures.  This commit therefore
fixes this comment.
Reported-by: NBart Van Assche <Bart.VanAssche@wdc.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NBart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: NLeon Romanovsky <leonro@mellanox.com>