cnic: Update the rcu_access_pointer() usages

1. Remove the rcu_read_lock/unlock around rcu_access_pointer
2. Replace the rcu_dereference with rcu_access_pointer

Signed-off-by: Tej Parkash <tej.parkash@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>