pasemi_mac: Clean TX ring in poll

Unfortunately there's no timeout for how long a packet can sit on
the TX ring after completion before an interrupt is generated, and
we want to have a threshold that's larger than one packet per interrupt.

So we have to have a timer that occasionally cleans the TX ring even
though there hasn't been an interrupt. Instead of setting up a dedicated
timer for this, just clean it in the NAPI poll routine instead.

[ Resolved conflicts with napi_struct changes... -DaveM ]

Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: David S. Miller <davem@davemloft.net>