i40e: don't allow i40e_vsi_(add|kill)_vlan to operate when VID<1

Now that we have the separate i40e_(add|rm)_vlan_all_mac functions, we
should not be using the i40e_vsi_kill_vlan or i40e_vsi_add_vlan
functions when PVID is set or when VID is less than 1. This allows us to
remove some checks in i40e_vsi_add_vlan and ensures that callers which
need to handle VID=0 or VID=-1 don't accidentally invoke the VLAN mode
handling used to convert filters when entering VLAN mode. We also update
the functions to take u16 instead of s16 as well since they no longer
expect to be called with VID=I40E_VLAN_ANY.

Change-ID: Ibddf44a8bb840dde8ceef2a4fdb92fd953b05a57
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>