staging: qlge: fix an error code in probe()

If alloc_etherdev_mq() fails then return -ENOMEM instead of success.
The "err = 0;" triggers an unused assignment now so remove that as
well.

Fixes: 953b9400 ("staging: qlge: Initialize devlink health dump framework")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/YFiyicHI189PXrha@mwanda


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>