drivers/net/virtio_net: Added basic RSS support.

Added features for RSS.
Added initialization, RXHASH feature and ethtool ops.
By default RSS/RXHASH is disabled.
Virtio RSS "IPv6 extensions" hashes disabled.
Added ethtools ops to set key and indirection table.

Signed-off-by: Andrew Melnychenko <andrew@daynix.com>
Link: https://lore.kernel.org/r/20220328175336.10802-3-andrew@daynix.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>