bhyve: Refactor pci_irq_route

[bnovkov]

Summary

Change pci_irq_route's arguments to a slot number and a pin number
instead of a pointer to an emulated PCI device instance.
This allows us to set up fixed IRQ mappings for slots without device
instances, which is a prerequisite for device hotplugging.
No functional change intended.

[markj]

Looks ok aside from the comments.

usr.sbin/bhyve/pci_emul.c

2152

What's the purpose of this change?

usr.sbin/bhyve/pci_irq.c

18

Extra newline

[bnovkov]

Address @markj 's comments.

usr.sbin/bhyve/pci_emul.c

2152

Ah, that was a leftover change from a previous version of this patch, removed.