net: ena: fix ena_com_fill_hash_function() implementation

ena_com_fill_hash_function() didn't configure the rss->hash_func.

Fixes: 1738cd3e

 ("net: ena: Add a driver for Amazon Elastic Network Adapters (ENA)")
Signed-off-by: Netanel Belgazal <netanel@amazon.com>
Signed-off-by: Sameeh Jubran <sameehj@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>