Add support to create tx traffic scheduling classes with specified
scheduling parameters.  Return an existing class if a match is found
with same scheduling parameters.
Signed-off-by: NRahul Lakkireddy <rahul.lakkireddy@chelsio.com>
Signed-off-by: NHariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>