ibmvnic: Allow device probe if the device is not ready at boot

Allow the device to be initialized at a later time if
it is not available at boot. The device will be allowed to probe but
will be given a "down" state. After completing device probe and
registering the net device, the driver will await an interrupt signal
from its partner device, indicating that it is ready for boot. The
driver will schedule a work event to perform the necessary procedure
and begin operation.

Co-developed-by: Thomas Falcon <tlfalcon@linux.ibm.com>
Signed-off-by: Thomas Falcon <tlfalcon@linux.ibm.com>
Signed-off-by: Cristobal Forno <cforno12@linux.ibm.com>
Acked-by: Lijun Pan <lijunp213@gmail.com>
Reviewed-by: Dany Madden <drt@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>