s390/pci: implement pcibios_release_device

Use pcibios_release_device to implement architecture-specific
functionality when a pci device is released. This function
will be called during pci_release_dev.

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