net: ena: ethtool: use correct value for crc32 hash

Up till kernel 4.11 there was no enum defined for crc32 hash in ethtool,
thus the xor enum was used for supporting crc32.

Fixes: 1738cd3e ("net: ena: Add a driver for Amazon Elastic Network Adapters (ENA)")
Signed-off-by: Sameeh Jubran <sameehj@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>