rtnetlink: verify rate parameters for calls to ndo_set_vf_rate

rtnetlink: verify rate parameters for calls to ndo_set_vf_rate

When calling ndo_set_vf_rate() the max_tx_rate parameter may be zero,
in which case the setting is cleared, or it must be greater or equal to
min_tx_rate.

Enforce this requirement on all calls to ndo_set_vf_rate via a wrapper
which also only calls ndo_set_vf_rate() if defined by the driver.

Based on work by Jakub Kicinski <[email protected]>

Signed-off-by: Bin Chen <[email protected]>
Signed-off-by: Baowen Zheng <[email protected]>
Signed-off-by: Simon Horman <[email protected]>
Signed-off-by: Paolo Abeni <[email protected]>