nfp: support VF rate limit with NFDK

Support VF rate limiting with NFDK by adding ndo_set_vf_rate to the NFDK
ops structure.

NFDK is used to communicate via PCIE to NFP-3800 based NICs
while NFD3 is used for other NICs supported by the NFP driver.
The VF rate limit feature is already supported by the driver for NFD3.

Signed-off-by: Bin Chen <bin.chen@corigine.com>
Reviewed-by: Baowen Zheng <baowen.zheng@corigine.com>
Reviewed-by: Louis Peens <louis.peens@corigine.com>
Signed-off-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>