i40e: Limit DCB FW version checks to X710/XL710 devices

X710/XL710 devices require FW version checks to properly handle DCB
configurations from the FW.  Newer devices do not, so limit these checks
to X710/XL710.

Signed-off-by: Greg Bowers <gregory.j.bowers@intel.com>
Acked-by: Shannon Nelson <shannon.nelson@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>