i40evf: refactor shutdown code

If the VF driver is running in the host, the shutdown code is completely
broken. We cannot wait in our down routine for the PF to respond to our
requests, as its admin queue task will never run while we hold the lock.

Instead, we schedule operations, then let the watchdog take care of
shutting things down. If the driver is being removed, then wait in the
remove routine until the watchdog is done before continuing.

Change-ID: I93a58d17389e8d6b58f21e430b56ed7b4590b2c5
Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Acked-by: Shannon Nelson <shannon.nelson@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>