net: microchip: sparx5: add support for offloading dscp table

Add support for offloading dscp app entries. Dscp values are global for
all ports on the sparx5 switch. Therefore, we replicate each dscp app
entry per-port.

Signed-off-by: Daniel Machon <daniel.machon@microchip.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>