net: core: dev: Add extack argument to __dev_change_flags()

In order to pass extack together with NETDEV_PRE_UP notifications, it's
necessary to route the extack to __dev_open() from diverse (possibly
indirect) callers. The last missing API is __dev_change_flags().

Therefore extend __dev_change_flags() with and extra extack argument and
update the two existing users.

Since the function declaration line is changed anyway, name the struct
net_device argument to placate checkpatch.

Signed-off-by: Petr Machata <petrm@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>