Creating the global workqueue during driver init may fail, deal with it.
Also, destroy the created workqueue on any subsequent error.

Fixes: 0f54761d ("qeth: Support VEPA mode")
Signed-off-by: NJulian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>