This commit removes the extraneous parentheses from rcu_assign_keypointer()
so that rcu_assign_pointer() can be wrapped in do-while.  It also wraps
rcu_assign_keypointer() in a do-while and parenthesizes its final argument,
as suggested by David Howells.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>