i40e: Convert CEE App TLV selector to IEEE selector

Changes the parsing of CEE App TLVs to fill in the App selector in struct
i40e_dcbx_config with the IEEE App selector so the caller doesn't have to
consider whether the App came from a CEE or IEEE DCBX negotiation.

Change-ID: Ia7d9d664cde04d2ebcc9822fd22e4929c6edab3a
Signed-off-by: Greg Bowers <gregory.j.bowers@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>