Add a module parameter wqm_quanta.  It controls the number of segments
transmitted at a time.
Signed-off-by: NSweta Bhatt <sweta.bhatt@einfochips.com>
Signed-off-by: NChien Tung <ctung@neteffect.com>
Signed-off-by: NRoland Dreier <rolandd@cisco.com>