[display] Remove ddk calls from on_displays_changed

This change replaces get_info with per-display argument structs to
on_displays_changed, and it moves the display mode validation to a
posted task. This allow simpler locking in the impl drivers, and it
enables the addition of output parameters into the argument structs.

This change also causes ownership messages to be sent before display
changed messages. Update various clients to not rely on a particular
order of messages.

Test: Boot to virtcon/hotplug on NUC/vim/eve. Run gfxtest, gfxlatency,
and display-test

Change-Id: Id561ed7587037353c1aeeab96511481d74026bdc

[display] Add display mode validation

Test: display-test on NUC and eve
Change-Id: Ic5f35bbd73b3d860d330cc94102009ab9ba8b45c

[display] Add layers to ddk display protocol

Change-Id: I0e876353121ca8c58bcca4a5c0ada6ee61d0e259

[ddk][display] Add support for non-edid displays

Change-Id: Idabcda75709659363deb31cead1f2b923a8b6fcc

[dev][virtio] Migrate virtio to display controller

Change-Id: I7f8afeacf7f4b229b91ca75e62f16a0bb10b1c08

[virtio] Wire BTIs through to the device objects

Change-Id: I8a19733734b8694f734463dd3134b77a9ae50d14

[virtio] Migrate GPU to io_buffer

Change-Id: Ie1d4db1290c1b0e303b862a133a4beeee43b4659

[virtio][gpu] Code cleanup

Change-Id: Ib141c88e9c6201c2a1def1f680c2e644514007cc

[virtio][gpu] Replace cnd_t with sem_t.

Patch up some race conditions that existed using cnd_t.

Change-Id: I3e9cb558a3ca695fea1c99696ba6745c82b71085

[virtio] Refactor virtio backend support

- Implement device backends for transport rather than having
it be a part of the device class itself. These backends are
plugged into the device class to provide an abstraction between
device level interfaces and the specific nuances around the
virtio interface.
- Implement a legacy virtio bar0 PIO interface for use in systems
that only provide Virtio 0.9.5 devices.
- Move logging away from VIRTIO_ERROR and use newer ddk zxlogf.
- Run clang-fmt and clean up small nits here and there.
Change-Id: I2568e9554378163f19b89537986e0d5ea8b47510

[zx] Magenta -> Zircon

The Great Renaming is here!

Change-Id: I3229bdeb2a3d0e40fb4db6fec8ca7d971fbffb94

[zircon][mxtl->fbl] Rename mxtl to fbl

Change-Id: Ie21b6498e1bfb0a7fa0315e40b9e5c3ee78646be

[ddk][display] new protocol support (9 of n)

Migrate MX_PROTOCOL_DISPLAY to new style

Change-Id: I02cd6b18a9d12a811d4a186caece963eea21203a

[udev][virtio] Move to system/dev/bus/

Change-Id: If774aaef5040c31b6ee76dad1aa8bac30165f045