Invoke the desc->handle_irq directly in the top-level dispatch,
just like other sophisticated ports.

This will allow us to decrease the cost of the MSI queue dispatch.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

We used to need this to compute virt_irq --> ino, but that
is no longer necessary.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

We have a place to stick INO information in the
virt_to_real_irq_table[], which is currently only used for VIRQs.
And that is readily accessible from the one __irq_ino() call site.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This also makes us use the MSI queues correctly.

Each MSI queue is serviced by a normal sun4u/sun4v INO interrupt
handler.  This handler runs the MSI queue and dispatches the
virtual interrupts indicated by arriving MSIs in that MSI queue.

All of the common logic is placed in pci_msi.c, with callbacks to
handle the PCI controller specific aspects of the operations.

This common infrastructure will make it much easier to add MSG
support.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>