net: thunderx: Receive hashing HW offload support

Adding support for receive hashing HW offload by using RSS_ALG
and RSS_TAG fields of CQE_RX descriptor. Also removed dependency
on minimum receive queue count to configure RSS so that hash is
always generated.

This hash is used by RPS logic to distribute flows across multiple
CPUs. Offload can be disabled via ethtool.

Signed-off-by: Robert Richter <rrichter@cavium.com>
Signed-off-by: Sunil Goutham <sgoutham@cavium.com>
Signed-off-by: Aleksey Makarov <aleksey.makarov@caviumnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>