kvm: extend kvm_irqchip_add_msi_route to work on s390

on s390 MSI-X irqs are presented as thin or adapter interrupts
for this we have to reorganize the routing entry to contain
valid information for the adapter interrupt code on s390.
To minimize impact on existing code we introduce an architecture
function to fixup the routing entry.

Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
