igc: set TP bit in 'supported' and 'advertising' fields of ethtool_link_ksettings

set TP bit in the 'supported' and 'advertising' fields. i225/226 parts
only support twisted pair copper.

Fixes: 8c5ad0da

 ("igc: Add ethtool support")
Signed-off-by: Prasad Koya <prasad@arista.com>
Acked-by: Sasha Neftin <sasha.neftin@intel.com>
Tested-by: Naama Meir <naamax.meir@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>