datapath: RCU dereference correct pointer in table.

datapath: RCU dereference correct pointer in table.

Our hash table implementation consists of two levels of buckets
and then arrays of pointers.  The bucket arrays are fixed by the
size of the table, which is therefore protected by the RCU
dereference of the table pointer.  The arrays change when items
are inserted or deleted.  However, in tbl_insert/remove we need
to look at the old values and we do an rcu_dereference() on the
second level array instead of the bucket itself.  Other places
that access the table for lookup do the pointer dereference in
the correct order.

Found by sparse.

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