[PATCH] natsemi: NAPI and a bugfix

As documented in National application note 1287 the RX state machine on
the natsemi chip can lock up under some conditions (mostly related to
heavy load).  When this happens a series of bogus packets are reported
by the chip including some oversized frames prior to the final lockup.

This patch implements the fix from the application note: when an
oversized packet is reported it resets the RX state machine, dropping
any currently pending packets.

Signed-off-by: Mark Brown <broonie@sirena.org.uk>
Signed-off-by: Jeff Garzik <jeff@garzik.org>