net: atlantic: QoS implementation: max_rate

This patch adds initial support for mqprio rate limiters (max_rate only).

Atlantic HW supports Rate-Shaping for time-sensitive traffic at per
Traffic Class (TC) granularity.
Target rate is defined by:
* nominal link rate (always 10G);
* rate factor (ratio between nominal rate and max allowed).

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>