igc: Set QBVCYCLET_S to 0 for TSN Basic Scheduling

According to datasheet section 8.12.19, when there's no TSN offloading
Shadow_QbvCycle bit[29:0] must be set to zero for basic scheduling.

Signed-off-by: Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@intel.com>
Tested-by: Dvora Fuxbrumer <dvorax.fuxbrumer@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/igc/igc_tsn.c

@@ -52,7 +52,7 @@ static int igc_tsn_disable_offload(struct igc_adapter *adapter)
 		wr32(IGC_ENDQT(i), NSEC_PER_SEC);
 	}
 
-	wr32(IGC_QBVCYCLET_S, NSEC_PER_SEC);
+	wr32(IGC_QBVCYCLET_S, 0);
 	wr32(IGC_QBVCYCLET, NSEC_PER_SEC);
 
 	adapter->flags &= ~IGC_FLAG_TSN_QBV_ENABLED;