datapath: Allow the number of hash entries to exceed TBL_MAX_BUCKETS

datapath: Allow the number of hash entries to exceed TBL_MAX_BUCKETS

* If the number of entries in a table exceeds
  the number of buckets that it has then
  an attempt will be made to resize the table.

* There is a limit of TBL_MAX_BUCKETS placed on
  the number of buckets of a table.

* If this limit is exceeded keep using the existing table.
  This allows a table to hold more than TBL_MAX_BUCKETS
  entries at the expense of increased hash collisions.

Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Jesse Gross <jesse@nicira.com>