smbios: handle smbios3 for arm64

Get smbios working on arm64 where it seems to be
exclusively smbios version 3.x

The "interesting" thing here is that the smbios table seems to be
RAM in the EFI runtime services table. This makes it owned by "ram0",
and not io memory. That prevents bus_alloc_resource() from being able
to claim it, since ram0 already owns it. According to jhb, this is
how things are supposed to work. Eg, bus_alloc_resource() is meant
to be used with IO memory, not physical memory. Following his
suggestion, I converted the driver to simply use pmap_mapbios().

This is a prerequisite for getting IPMI to attach via the SSIF
attachment on arm64 servers, where all IPMI that I've seen
uses SSIF.

Note that this change is based on initial work by Allan Jude in
https://reviews.freebsd.org/D28739.

Reviewed by: imp
Sponsored by: Netflix, Ampere Computing LLC (D28739)
Differential Revision: https://reviews.freebsd.org/D42592

sys: Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

abstract out the vm detection via smbios..

This makes the detection of VMs common between platforms that
have SMBios.

Reviewed by: imp, kib
Differential Revision: https://reviews.freebsd.org/D38800

ipmi,smbios: move smbios_walk_table to smbios.h

This function will be used for exposing DMI info as sysctls in the
smbios module (in an upcoming review).

While here, add __packed to the structs.

Reviewed by: dab
MFC after: 1 week
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D29270

Revert "ipmi_smbios: Deduplicate smbios entry point discovery logic"

This depends on another commit that has not landed yet, and broke the build

This reverts commit ba6e37e47f41484fc61cc034619267b82ddd056c.

ipmi_smbios: Deduplicate smbios entry point discovery logic

Sponsored by: Ampere Computing LLC
Submitted by: Klara Inc.
Reviewed by: imp
Differential Revision: https://reviews.freebsd.org/D28743

smbios: Move smbios driver out from x86 machdep code

Add it to the x86 GENERIC and MINIMAL kernels

Sponsored by: Ampere Computing LLC
Submitted by: Klara Inc.
Reviewed by: rpokala
Differential Revision: https://reviews.freebsd.org/D28738