ice: Update comment for ice_fltr_mgmt_list_entry

Previously the comment stated that VSI lists should be used when a
second VSI becomes a subscriber to the "VLAN address". VSI lists
are always used for VLAN membership, so replace "VLAN address" with
"MAC address". Also note that VLAN(s) always use VSI list rules.

Signed-off-by: Brett Creeley <brett.creeley@intel.com>
Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>