pseries: Add PCI MSI/MSI-X support

pseries: Add PCI MSI/MSI-X support

This patch implements MSI and MSI-X support for the pseries PCI host
bridge.  To do this it adds:

 * A "config_space_address to msi_table" map, since the MSI RTAS calls
take a PCI config space address as an identifier.

 * A MSIX memory region to catch msi_notify()/msix_notiry() from
virtio-pci and pass them to the guest via qemu_irq_pulse().

 * RTAS call "ibm,change-msi" which sets up MSI vectors for a
device. Note that this call may configure and return lesser number of
vectors than requested.

 * RTAS call "ibm,query-interrupt-source-number" which translates MSI
vector to interrupt controller (XICS) IRQ number.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
[agraf: fix error case ndev < 0]
Signed-off-by: Alexander Graf <agraf@suse.de>