As the name suggests ETH_RSS_HASH_NO_CHANGE is received upon changing
the key or indirection table using ethtool while keeping the same hash
function.

Also add a function for retrieving the current hash function from
the ena-com layer.

Fixes: 1738cd3e ("net: ena: Add a driver for Amazon Elastic Network Adapters (ENA)")
Signed-off-by: NSameeh Jubran <sameehj@amazon.com>
Signed-off-by: NSaeed Bshara <saeedb@amazon.com>
Signed-off-by: NArthur Kiyanovski <akiyano@amazon.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>