igc: Fix static checker warning

drivers/net/ethernet/intel/igc/igc_mac.c:424 igc_check_for_copper_link()
error: uninitialized symbol 'link'.
This patch come to fix this warning and initialize the 'link' symbol.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 707abf06 ("igc: Add initial LTR support")
Signed-off-by: Sasha Neftin <sasha.neftin@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>