datapath: Directly use methods for protecting RCU/RTNL data.

datapath: Directly use methods for protecting RCU/RTNL data.

We currently have a wrapper to protect the datapath ports array.
However, this can lead to confusion over exactly what lock is
protecting the access (either RTNL or RCU).  This removes the
wrapper in favor of directly accessing the data, which also has
the benefit of being less permissive about what lock we allow so
it can be restricted to the one that we expect.

Signed-off-by: Jesse Gross <jesse@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>