e1000e: tx_timeout should not increment for non-hang events

e1000e: tx_timeout should not increment for non-hang events

Currently the driver increments the tx_timeout counter (an error counter)
when simply resetting the part with outstanding transmit work pending.
This is an unnecessary count of an error, when all we should be doing is
just resetting the part and discarding the transmits.  With this change the
only increment of tx_timeout is when the stack calls the watchdog reset
function due to a true Tx timeout.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Reviewed-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>