net: dsa: felix: configure default-prio and dscp priorities

net: dsa: felix: configure default-prio and dscp priorities

Follow the established programming model for this driver and provide
shims in the felix DSA driver which call the implementations from the
ocelot switch lib. The ocelot switchdev driver wasn't integrated with
dcbnl due to lack of hardware availability.

The switch doesn't have any fancy QoS classification enabled by default.
The provided getters will create a default-prio app table entry of 0,
and no dscp entry. However, the getters have been made to actually
retrieve the hardware configuration rather than static values, to be
future proof in case DSA will need this information from more call paths.

For default-prio, there is a single field per port, in ANA_PORT_QOS_CFG,
called QOS_DEFAULT_VAL.

DSCP classification is enabled per-port, again via ANA_PORT_QOS_CFG
(field QOS_DSCP_ENA), and individual DSCP values are configured as
trusted or not through register ANA_DSCP_CFG (replicated 64 times).
An untrusted DSCP value falls back to other QoS classification methods.
If trusted, the selected ANA_DSCP_CFG register also holds the QoS class
in the QOS_DSCP_VAL field.

The hardware also supports DSCP remapping (DSCP value X is translated to
DSCP value Y before the QoS class is determined based on the app table
entry for Y) and DSCP packet rewriting. The dcbnl framework, for being
so flexible in other useless areas, doesn't appear to support this.
So this functionality has been left out.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>