ice: Add space to unknown speed

Add space to the end of 'Unknown' string  in  order to avoid
concatenation with 'bps' string when formatting netdev log message.

Signed-off-by: Simon Perron Caissy <simon.perron.caissy@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>