i40e: remove WQ_UNBOUND and the task limit of our workqueue

During certain events such as a CORER, multiple devices will run a work
task to handle some cleanup. This can cause issues due to
a single-threaded workqueue which can mean that a device doesn't cleanup
in time. Prevent this by removing the single-threaded restriction on the
module workqueue. This avoids the need to add more complex yielding
logic in our service task routine. This is also similar to what other
drivers such as fm10k do.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>