igc: Fix Supported Pause Frame Link Setting

The Supported Pause Frame always display "No" even though the Advertised
pause frame showing the correct setting based on the pause parameters via
ethtool. Set bit in link_ksettings to "Supported" for Pause Frame.

Before output:
Supported pause frame use: No

Expected output:
Supported pause frame use: Symmetric

Fixes: 8c5ad0da

 ("igc: Add ethtool support")
Signed-off-by: Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@intel.com>
Reviewed-by: Malli C <mallikarjuna.chilakala@intel.com>
Tested-by: Dvora Fuxbrumer <dvorax.fuxbrumer@linux.intel.com>
Acked-by: Sasha Neftin <sasha.neftin@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>