net/mlx5: E-Switch, Refactor chains and priorities

To support the entire chain and prio range (32bit + 16bit),
instead of a using a static array of chains/prios of limited size, create
them dynamically, and use a rhashtable to search for existing chains/prio
combinations.

This will be used in next patch to actually increase the number using
unamanged tables support and ignore flow level capability.

Signed-off-by: Paul Blakey <paulb@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Reviewed-by: Oz Shlomo <ozsh@mellanox.com>
Reviewed-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>