vtscmi: Add a virtio-scmi driver

Add a new virtio backend to support SCMI VirtIO devices (type 32) as
defined by the VirtIO specification since version v1.2.

https://docs.oasis-open.org/virtio/virtio/v1.2/cs01/virtio-v1.2-cs01.pdf

Reviewed by: andrew, bryanv
Sponsored by: Arm Ltd
Differential Revision: https://reviews.freebsd.org/D43047

Add a virtio-gpu 2D driver

Add a driver to connect vt to the VirtIO GPU device in 2D mode. This
provides a output on the display when a qemu virtio gpu device is
added, e.g. with -device virtio-gpu-pci.

Tested on qemu using UTM, and a Hetzner arm64 VM instance.

Reviewed by: bryanv (earlier version)
Sponsored by: Arm Ltd
Differential Revision: https://reviews.freebsd.org/D40094

acpi_ged: New driver to ACPI generic event device

New driver to ACPI generic event device, defined in ACPI spec.
Some ACPI power button may not work without this.

In qemu arm64 with "virt" machine, with ACPI firmware,
enable devd check devd message by
and invoke following command in qemu monitor
(qemu) system_powerdown
and make sure some power button input event appear.
(setting sysctl hw.acpi.power_button_state=S5 is not work,
because ACPI tree does not have \_S5 object.)

Reviewed by: andrew, hrs
Differential Revision: https://reviews.freebsd.org/D37032

arm64: Add per SoC family kernel config

There is multiple reason for this :
- This makes it easier to see which driver is needed for each SoC
- This makes it easier to create a custom config for one SoC
- This really reduce boot time (which some people might want)

Some explaination about the files :
- std.arm64 contains all standard kernel option
- std.dev contains all the standard kernel devices
- std.<soc> contains all drivers needed to boot on this SoC family
- <SOC> includes std.arm64, std.dev and std.<soc>
- GENERIC includes std.arm64, std.dev and all std.<soc>

Sponsored by: Diablotin Systems
MFC After: 2 months
Reviewed by: mmel, cognet, imp
Differential Revision: https://reviews.freebsd.org/D30474