vlan: vlan device not reading gso max size of parent.

The vlan devices are not reading the gso max size of the parent device.  As
a result devices that do not support 64K max gso size are currently
failing.

This issue is seen on 2.6.26 kernels as well and the same patch should be
able to be applied without any issues.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>