BugLink: http://bugs.launchpad.net/bugs/1616677

struct netvsc_device is destroyed on mtu change so keeping the
protection flag there is not a good idea. Move it to struct
net_device_context which is preserved.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit f580aec4)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Acked-by: Kamal Mostafa <kamal@canonical.com>