spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

bhyve: add cmdline option for user defined fw_cfg items

Some guest allow to configure themself by fw_cfg. E.g. Fedora CoreOs can
be provisioned by adding a JSON file as fw_cfg item.

Reviewed by: jhb
MFC after: 1 week
Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D38338

bhyve: make use of qemus acpi table loader

Add all acpi tables to qemus acpi table loader. This passes the acpi
tables by fwcfg to the guest.

Reviewed by: markj
MFC after: 1 week
Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D38439

bhyve: Accept a variable-length string name for qemu_fwcfg_add_file.

It is illegal (UB?) to pass a shorter array to a function argument
that takes a fixed-length array. Do a runtime check for names that
are too long via strlen() instead.

Reviewed by: markj
Reported by: GCC -Wstringop-overread
Differential Revision: https://reviews.freebsd.org/D39211

bhyve: add helper for adding fwcfg files

Fwcfg items without a fixed index are reported by the file_dir. They
have an index of 0x20 and above. This helper simplifies the addition of
such fwcfg items. It selects a new free index, assigns it to the fwcfg
items and creates an proper entry in the file_dir.

Reviewed by: markj
MFC after: 1 week
Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D38336

bhyve: add common fwcfg items

Qemu defines some common fwcfg items. We don't need to support all of
them. Only a subset needs to be present for fwcfg to work properly.

- signature
The signature is used by the guest to check if qemu's fwcfg is
available or not.
- id
The id is used by the guest to check which features are supported by
the fwcfg implementation of the hypervisor.
- file_dir
The file dir reports all fwcfg items which don't have a fixed index.
These are mostly user defined fwcfg items.

Reviewed by: <If someone else reviewed your modification.>
MFC after: 1 week
Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D38335

bhyve: add emulation for qemu's fwcfg data port

The data port returns the data of the fwcfg item.

Reviewed by: markj
MFC after: 1 week
Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D38333

bhyve: add basic qemu fwcfg implementation

qemu's fwcfg and bhyve's fwctl are both used to configure ovmf. qemu's
fwcfg is much more powerfull than bhyve's fwctl. For that reason, add
support for qemu's fwcfg.

Reviewed by: markj
MFC after: 1 week
Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D38331