i40e: Clarify steps in MAC/VLAN filters initialization routine

i40e: Clarify steps in MAC/VLAN filters initialization routine

This patch clarifies the reason for removal of automatically
firmware-generated filter and explicit addition of filter which
accepts frames with any VLAN id.

Change-ID: Iabf180b6d61c4d8a36d3bcf8457c377a6f2aca0e
Signed-off-by: Filip Sadowski <filip.sadowski@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Orabug: 26132523
(cherry picked from commit 3954b39102677c879d7663621fb9a7e0da349274)
Signed-off-by: Jack Vogel <jack.vogel@oracle.com>
Reviewed-by: Brian Maly <brian.maly@oracle.com>