ice: Remove boolean vlan_promisc flag from function

Currently, the vlan_promisc flag is used exclusively by VF VSI to
determine whether or not to toggle VLAN pruning along with
trusted/true-promiscuous mode. This is not needed for a couple of
reasons. First, trusted/true-promiscuous mode is only supposed to allow
all MAC filters within VLANs that a VF has added filters for, so VLAN
pruning should not be disabled. Second, the boolean argument makes the
function confusing and unintuitive. Remove this flag.

Signed-off-by: Brett Creeley <brett.creeley@intel.com>
Tested-by: Tony Brelinski <tony.brelinski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>