Since commit29a5dcae27("nfp: flower: offload phys port MTU change") we take encapsulation headroom into account when calculating the max allowed MTU. This is unnecessary as the max MTU advertised by firmware should have already accounted for encap headroom. Subtracting headroom twice brings the max MTU below what's necessary for some deployments. Fixes:29a5dcae27("nfp: flower: offload phys port MTU change") Signed-off-by: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com> Reviewed-by: John Hurley <john.hurley@netronome.com> Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com> Signed-off-by: David S. Miller <davem@davemloft.net>