TI Davinci EMAC : Fix Console Hang when bringing the interface down

In the NAPI poll function(emac_poll), check for netif_running()
is unnecassary. In addition to associated runtime overhead, it
also results in a continuous softirq loop when the interface is
brought down under heavy traffic(tested wit Traffic Generator).
Once the interface is disabled, the poll function always returns
zero(with the check for netif_running) and napi_complete() would
never get called resulting in softirq loop.

Signed-off-by: Sriramakrishnan <srk@ti.com>
Acked-by: Chaithrika U S <chaithrika@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>