i40e/i40evf: Faster RX via avoiding FCoE

As it turns out, calling into other files from hot path hurts
performance a lot.  In this case the majority of the time we
call "check FCoE" and the packet is *not* FCoE, but this call
was taking 5% of our total cycles spent on receive.

Change-ID: I080552c26e7060bc7b78504dc2763f6f0b3d8c76
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>