iavf: wait longer for close to complete

On some hardware/driver/architecture combinations, it may take longer
than 200msec for all close operations to be completed, causing a
spurious error message to be logged.

Increase the timeout value to 500msec to avoid this erroneous error.

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>