i40e: increase AQ work limit

With 64 VFs, we can easily overwhelm the AQ on the PF if we have too low
a limit on the number of AQ requests. This leads to ARQ overflow errors,
and occasionally VFs that fail to initialize.

Since we really only hit this condition on initial VF driver load, the
requests that we process are lightweight, so this extra work doesn't
cause problems for the PF driver.

Change-ID: I620221520d8af987df6ace9ba938ffaf22107681
Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>