sys: Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

dtb: Be much less verbose in the building of dtb

Make the dtb/dtbo files with less noise. Remove echo statements, but add
back the call for the non-meta builds to replace the removed noise.

Suggetions by: jrtc27
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D37073

Switch to the new device-tree vendor tree

The old vendor tree was never fully merged and doing partial merge isn't
supported with git subtree merge so a new one was created.
Switch the build to use the new DTS from sys/contrib/device-tree
This also bump the DTS used to be in sync with Linux 5.9
While here change the way to get the linux version, simply hardcode
the value in sys/dts/freebsd-compatible.dts and use awk to get that
to put it in the CFLAGS.
As a bonus we now have the bindings docs available
in sys/contrib/device-tree/Bindings/ so no need to link to the Linux repo
or to the vendor tree.

Use MACHINE_CPUARCH when checking for arm64

Use MACHINE_CPUARCH with arm64 (aarch64) when we build code that could run
on any 64-bit Arm instruction set. This will simplify checks in downstream
consumers targeting prototype instruction sets.

The only place we check for MACHINE_ARCH == aarch64 is when building the
device tree blobs. As these are targeting current generation ISAs.

Sponsored by: Innovate UK
Differential Revision: https://reviews.freebsd.org/D26370

Introduce bsd.sysdir.mk to consolidate looking for the kernel.

Reviewed by: jhb
Differential Revision: https://reviews.freebsd.org/D22144

fdt: Fix installation of aarch64 dtb

r345519 rewrote parts of how we build .dtb, but mistakenly dropped the
vendor dir for aarch64. Simply drop the :T for building ${DTB} in the
aarch64 case- it'll get applied at install-time as-needed, with :H:T for
determining the vendor dir.

Reported by: manu
Tested by: manu
Reviewed by: manu
MFC after: 3 days

fdt: stop installing FDT_DTS_FILE

r346307 inadvertently started installing FDT_DTS_FILE along with the kernel.
While this isn't necessarily bad, it was not intended or discussed and it
actively breaks some current setups that don't anticipate any .dtb being
installed when it's using static fdt. This change could be reconsidered down
the line, but it needs to be done with prior discussion.

Fix it by pushing FDT_DTS_FILE build down into the raw dtb.build.mk bits.
This technically allows modules building DTS to accidentally specify an
FDT_DTS_FILE that gets built but isn't otherwise useful (since it's not
installed), but I suspect this isn't a big deal and would get caught with
any kind of testing -- and perhaps this might end up useful in some other
way, for example by some module wanting to embed fdt in some other way than
our current/normal mechanism.

Reported by: Mori Hiroki <yamori813@yahoo.co.jp>
MFC after: 3 days
X-MFC-With: r346307

Allow kernel config to specify DTS/DTSO to build, and out-of-tree support

This allows for directives such as

makeoptions DTS+=/out/of/tree/myboard.dts
# in tree! Same rules applied as if this were in a dtb/ module
makeoptions DTS+=otherboard.dts

to be specified in config(5) and have these built/installed alongside th
kernel. The assumption that overlays live in an overlays/ directory is only
made for in-tree DTSO, but we still make the assumption that out-of-tree
arm64 DTS will be in vendored directories (for now).

This lowers the cost to hacking on an overlay or dts by being able to
quickly throw it in a custom config, especially if it doesn't fit one of the
current dtb/modules quite appropriately or it's not intended for commit
there.

The build/install targets were split out of dtb.mk to centralize the build
logic and leave out the all/realinstall/CLEANFILES additions... it was
believed that we didn't want to pollute the kernel build with these.

The build rules were converted to suffix rules at the suggestion of Ian to
clean things up a little bit in a world where we can have mixed
in-tree/out-of-tree DTS/DTSO specified.

Reviewed by: ian
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D19351