mlxsw: spectrum: Track lossiness in struct mlxsw_sp_hdroom

Client-side configuration has lossiness as an attribute of a priority.
Therefore add a "lossy" attribute to struct mlxsw_sp_hdroom_prio.

To a Spectrum ASIC, lossiness is a feature of a port buffer. Therefore add
struct mlxsw_sp_hdroom_buf, which in the following patches will get more
attributes, but right now only use it to track port buffer lossiness.

Instead of passing around the primary indicators of PFC and pause_en, add a
function mlxsw_sp_hdroom_bufs_reset_lossiness() to compute the buffer
lossiness from the priority map and priority lossiness. Change
mlxsw_sp_port_headroom_set() to take the buffer lossy flag from the
headroom configuration. Have the PFC and pause handlers configure priority
lossiness in mlxsw_sp_hdroom, from where it will propagate.

Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>