iavf: Fix updating statistics

Commit bac84861 ("iavf: Refactor the watchdog state machine") inverted
the logic for when to update statistics. Statistics should be updated when
no other commands are pending, instead they were only requested when a
command was processed. iavf_request_stats() would see a pending request
and not request statistics to be updated. This caused statistics to never
be updated; fix the logic.

Fixes: bac84861

 ("iavf: Refactor the watchdog state machine")
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>