Use the current logging style.

Add #define pr_fmt and remove embedded prefix from formats.

Not converting the current pr_<level> uses to netdev_<level>
because all the output here is nicely prefaced with "8021q: ".

Remove __func__ use from proc registration failure message.
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>