i40e: remove duplicate add/delete adminq command code for filters

We duplicate some code around adding and deleting filters using the
adminq interface. This is prone to errors in case there are bugs. Use
functions which extract the logic to their own portion so that we don't
duplicate it twice in code.

Change-ID: I60d68aeb887976787dec00b23ab386a106e61465
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>