netdev: Remove warning from __netif_schedule().

It isn't helping anything and we aren't going to be able to change all
the drivers that do queue wakeups in strange situations.

Just letting a noop_qdisc get scheduled will work because when
qdisc_run() executes via net_tx_work() it will simply find no packets
pending when it makes the ->dequeue() call in qdisc_restart.

Signed-off-by: David S. Miller <davem@davemloft.net>