s390/pci: improve pci hotplug

s390/pci: improve pci hotplug

PCI hotplug events basically notify about the new state of a
function. Unfortunately some hypervisors implement hotplug
events in a way where it is not clear what the new state of
the function should be.

Use clp_get_state to find the current state of the function
and handle accordingly.

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>