s390/pci: remove clp_rescan_pci_devices()

there is only one call site of clp_rescan_pci_devices() and
all the function does is call zpci_remove_reserved_devices()
followed by a duplicating clp_scan_pci_devices().
So inline the single call as a call to zpci_remove_reserved_devices()
and clp_scan_pci_devices() and remove the function.

Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>