net: net_device flags is an unsigned int

commit b00055aa ([NET] core: add RFC2863 operstate) changed
net_device flags from unsigned short to unsigned int.

Some core functions still assume its an unsigned short.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>