e1000e: update Tx Unit hang detection message

The Tx unit hang detection code in e1000e detects other hangs caused by
hardware components (e.g. Rx, DMA units), but it is not possible to detect
exactly which component is hung so it has always assumed a Tx unit hang.
When dumping a message to the system log because of a hang, this patch adds
more data to help narrow the cause of the issue and makes the message
non-Tx-specific.  Because this new code reads PHY registers which can
sleep, move it off to a workqueue.  This and all previously existing work
tasks in the driver are now cancelled when the driver is removed.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>