myri10ge: disable NAPI on failure to setup the interface

Disable NAPI if a failure occurs when setting up the interface. Leaving
it enabled could cause a BUG the next time an ifconfig up is issued.

Signed-off-by: Brice Goglin <brice@myri.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>