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: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>