r8169: call netif_napi_del at errpaths and at driver unload

when register_netdev fails, the init'ed NAPIs by netif_napi_add must be
deleted with netif_napi_del, and also when driver unloads, it should
delete the NAPI before unregistering netdevice using unregister_netdev.

Signed-off-by: Devendra Naga <devendra.aaru@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>