ibmvnic: Check adapter state during ibmvnic_poll

We do not want to process any receive frames if the ibmvnic_poll
routine is invoked while a reset is in process. Also, before
replenishing the rx pools in the ibmvnic_poll, we want to
make sure the adapter is not in the process of closing.

Signed-off-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>