i40e: Remove unused i40e_del_filter

The last use of i40e_del_filter() was removed in 2016 by
commit 9569a9a4 ("i40e: when adding or removing MAC filters, correctly
handle VLANs")

Remove it.

Fix up a comment that referenced it.

Note: The __ version of this function is still used.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Reviewed-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://patch.msgid.link/20250102173717.200359-7-linux@treblig.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>