mlxsw: spectrum: Initialize egress scheduling

Before introducing support for DCB ops we should first make sure we
initialize the relevant parts in the device correctly. Specifically, the
egress scheduling.

The device supports a superset of the 802.1Qaz standard with 4 hierarchy
levels that can be linked to each other in multiple ways and with
different transmission selection algorithms (TSA) employed between them.

However, since we only intend to support the 802.1Qaz standard we
flatten the hierarchies and let the user configure via DCB ops the TSA
and max rate shaper at the subgroup hierarchy (see figure below) and the
mapping between switch priority to traffic class. By default, all switch
priorities are mapped to traffic class 0, strict priority is employed
and max shaper is disabled.

Default configuration:

         switch priority 0      ...         switch priority 7
                 +                                  +
                 |                                  |
                 +----------------------------------+
                 |
              +--v--+                          +-----+
Traffic Class |     |                          |     |
  Hierarchy   | TC0 |           ...            | TC7 |
              |     |                          |     |
              +--+--+                          +--+--+
                 |                                |
              +--v--+                          +--v--+
  Subgroup    | SG0 |                          | SG7 |
  Hierarchy   |     |                          |     |
              +-----+                          +-----+
              | TSA |                          | TSA |
              +-----+           ...            +-----+
              | MAX |                          | MAX |
              +--+--+                          +--+--+
                 |                                |
                 +---------------+----------------+
                                 |
                              +--v--+
                      Group   |     |
                    Hierarchy | GR0 |
                              |     |
                              +--+--+
                                 |
                              +--v--+
                      Port    |     |
                    Hierarchy | PR0 |
                              |     |
                              +-----+

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>