devices: virtio: Introduce Virtio transport medium type for interrupt abstraction
devices: virtio: Introduce Virtio transport medium type for interrupt abstraction

Virtio, by spec definition, can operate using multiple transport medium
e.g. PCI, MMIO etc. In preparation for adding another transport medium
introduce Virtio transport type abstraction to do proper distinction
while setting up interrupts.

BUG=b:189182339
TEST=boot manatee and verify that Virtio PCI IRQ works properly

Change-Id: I6b8993e10f0a8edd3d3776322939f3dca70048c4
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/3855003
Tested-by: Tomasz Nowicki <a1603cf6334574df9b8204692b318701aeaf1ca1@google.com>
Reviewed-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>
Commit-Queue: Tomasz Nowicki <a1603cf6334574df9b8204692b318701aeaf1ca1@google.com>

google/crosvm,google/crosvm,google/crosvm,google/crosvm