sky2: force receive checksum when using RSS on some hardware (v2)

Found when reviewing the vendor driver. Apparently some chip versions
require receive checksumming to be enabled in order for RSS to work.

Also, if fix_features has to change some settings; put in message
in log in similar manner to netdev_fix_features.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>