ionic: remove noise from ethtool rxnfc error msg

It seems that ethtool is calling into .get_rxnfc more often with
ETHTOOL_GRXCLSRLCNT which ionic doesn't know about.  We don't
need to log a message about it, just return not supported.

Fixes: aa319881

 ("ionic: Add RSS support")
Signed-off-by: Shannon Nelson <shannon.nelson@amd.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>