octeontx2-pf: Support to change VLAN based RSS hash options via ethtool

Add support to control rx-flow-hash based on VLAN.
By default VLAN plus 4-tuple based hashing is enabled.
Changes can be done runtime using ethtool

To enable 2-tuple plus VLAN based flow distribution
  # ethtool -N <intf> rx-flow-hash <prot> sdv
To enable 4-tuple plus VLAN based flow distribution
  # ethtool -N <intf> rx-flow-hash <prot> sdfnv

Signed-off-by: George Cherian <george.cherian@marvell.com>
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>