igb: avoid transmit queue timeout in xdp path

Since we share the transmit queue with the network stack,
it is possible that we run into a transmit queue timeout.
This will reset the queue.
This happens under high load when XDP is using the
transmit queue pretty much exclusively.

netdev_start_xmit() sets the trans_start variable of the
transmit queue to jiffies which is later utilized by dev_watchdog(),
so to avoid timeout, let stack know that XDP xmit happened by
bumping the trans_start within XDP Tx routines to jiffies.

Fixes: 9cbc948b ("igb: add XDP support")
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Sven Auhagen <sven.auhagen@voleatech.de>
Tested-by: Sandeep Penigalapati <sandeep.penigalapati@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>