igc: Use strict cycles for Qbv scheduling

Configuring strict cycle mode in the controller forces more well
behaved transmissions when taprio is offloaded.

When set this strict_cycle and strict_end, transmission is not
enabled if the whole packet cannot be completed before end of
the Qbv cycle.

Fixes: 82faa9b7

 ("igc: Add support for ETF offloading")
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Signed-off-by: Aravindhan Gunasekaran <aravindhan.gunasekaran@intel.com>
Signed-off-by: Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@intel.com>
Tested-by: Naama Meir <naamax.meir@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>