net: atlantic: QoS implementation: min_rate

This patch adds support for mqprio min_rate limiters.

A2 HW supports Weighted Strict Priority (WSP) arbitration for Tx Descriptor
Queue scheduling among TCs, which can be used for min_rate shaping.

Signed-off-by: Mark Starovoytov <mstarovoitov@marvell.com>
Signed-off-by: Igor Russkikh <irusskikh@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>