rcu: Update from rcu_expedited variable to rcu_gp_is_expedited()

This commit updates open-coded tests of the rcu_expedited variable
to instead use rcu_gp_is_expedited().

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

diff --cc kernel/rcu/srcu.c
Simple merge

diff --cc kernel/rcu/tree.c
Simple merge

diff --cc kernel/rcu/tree_plugin.h
Simple merge