s390/pci: use adapter interrupt vector helpers

Make use of the adapter interrupt helpers in the PCI code. This is
the first step to convert the MSI interrupt code to PCI domains.
The patch removes the limitation of 64 adapter interrupts per
PCI function.

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