igc: Avoid transmit queue timeout for XDP

High XDP load triggers the netdev watchdog:

|NETDEV WATCHDOG: enp3s0 (igc): transmit queue 2 timed out

The reason is the Tx queue transmission start (txq->trans_start) is not updated
in XDP code path. Therefore, add it for all XDP transmission functions.

Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
Tested-by: Naama Meir <naamax.meir@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>