When hardware has trouble with a particular filter, we delete it from
the list. Unfortunately, we did not properly update the per-filter
statistic when doing so.

Create a helper function to handle this, and properly reduce the
necessary counter so that it tracks the number of active filters
properly.
Signed-off-by: NJacob Keller <jacob.e.keller@intel.com>
Tested-by: NAndrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>