This improves AEN handler for Host Network Controller Driver Status
Change (HNCDSC):

   * The channel's lock should be hold when accessing its state.
   * Do failover when host driver isn't ready.
   * Configure channel when host driver becomes ready.
Signed-off-by: NGavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>