i40e: Store lan_vsi_idx and lan_vsi_id in the right size

lan_vsi_idx and lan_vsi_id are assigned to u16 data sized variables but
declared in u8. This patch fixes the width of the datatype.

Change-ID: If4bcbcc7d32f2b287c51cb33d17879691258dce2
Signed-off-by: Pandi Kumar Maharajan <pandi.maharajan@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>