Revised version of the forcedeth NAPI support.
This version is based against netdev-2.6#upstream
(after the MAC patches from Ayaz today).

Can't use nv_disable_hw_interrupts because NAPI only wants to
mask off receive irq's and leave the others alone.
Signed-off-by: NStephen Hemminger <shemminger@osdl.org>
Signed-off-by: NJeff Garzik <jeff@garzik.org>