Add two hash functions to distribute RoCE v2 UDP source and Flowlabel
symmetrically. These are user visible API and any change in the
implementation needs to be tested for inter-operability between old and
new variant.

Link: https://lore.kernel.org/r/20200504051935.269708-2-leon@kernel.orgSigned-off-by: Mark Zhang <markz@mellanox.com>
Reviewed-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>