net/sonic: Remove redundant netif_start_queue() call

The transmit queue must be running already otherwise sonic_send_packet()
would not have been called. If the queue was stopped by the interrupt
handler, the interrupt handler will restart it again.

Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>