i40e: avoid O(n^2) loop when deleting all filters

Use __i40e_del_filter instead of using i40e_del_filter() which will
avoid doing an additional search to delete a filter we already have the
pointer for.

Change-ID: Iea5a7e3cafbf8c682ed9d3b6c69cf5ff53f44daf
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>