This fixes the issue that dev gro_max_size and gso_ipv4_max_size
can be set to a huge value:

  # ip link add dummy1 type dummy
  # ip link set dummy1 gro_max_size 4294967295
  # ip -d link show dummy1
    dummy addrgenmode eui64 ... gro_max_size 4294967295

Fixes: 0fe79f28 ("net: allow gro_max_size to exceed 65536")
Fixes: 9eefedd5 ("net: add gso_ipv4_max_size and gro_ipv4_max_size per device")
Reported-by: Xiumei Mu <xmu@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>