extend GSI IRQ routing to take a device ID

For ITS emulation we need the device ID along with the MSI payload
and doorbell address to identify an MSI, so we need to put it in the
GSI IRQ routing table too.
There is a per-VM capability by which the kernel signals the need for
a device ID, so check this and put the device ID into the routing
table if needed.
For PCI devices we take the bus/device/function triplet and and that
to the routing setup call.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>