octeontx2-pf: Add egress PFC support

octeontx2-pf: Add egress PFC support

As of now all transmit queues transmit packets out of same scheduler
queue hierarchy. Due to this PFC frames sent by peer are not handled
properly, either all transmit queues are backpressured or none.
To fix this when user enables PFC for a given priority map relavant
transmit queue to a different scheduler queue hierarcy, so that
backpressure is applied only to the traffic egressing out of that TXQ.

Signed-off-by: Suman Ghosh <sumang@marvell.com>
Link: https://lore.kernel.org/r/20220830120304.158060-1-sumang@marvell.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>