s390/pci: improve handling of bus resources

Cleanup the functions for allocation and setup of bus resources. Do
not allocate the same name for each resource but use a per-bus name.
Also provide means to cleanup all resources allocated by a bus.

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>