ixgbe: apply different rules for setting FC on E610

E610 device doesn't support disabling FC autonegotiation.

Create dedicated E610 .set_pauseparam() implementation and assign
it to ixgbe_ethtool_ops_e610.

Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Jedrzej Jagielski <jedrzej.jagielski@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Bharath R <bharath.r@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>