ixgbevf: Use a private workqueue to avoid certain possible hangs

ixgbevf: Use a private workqueue to avoid certain possible hangs

Orabug: 23177316

Use a private workqueue to avoid hangs that were otherwise possible
when performing stress tests, such as creating and destroying many
VFS repeatedly.

Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
Tested-by: Darin Miller <darin.j.miller@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
(cherry picked from commit 40a13e2493c9882cb4d09054d81a5063cd1589a2)
Signed-off-by: Brian Maly <brian.maly@oracle.com>