The DRM generic code started to import this header directly in Linux
6.12.x. Let's move the definition of `ARRAY_SIZE()` (the only thing that
<linux/array_size.h> defines) to this header.

Also, include <linux/array_size.h> from the same headers as Linux. This
includes <linux/kernel.h>, so the change should not break anything.

Reviewed by:	bz
Sponsored by:	The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D56570

... from <linux/compiler.h>.

<linux/wordpart.h> is the header defining them on Linux 6.12 (I didn't
check older versions).

<linux/wordpart.h> is also included from <linux/kernel.h>.

The DRM generic code started to depend on <linux/wordpart.h> in Linux
6.12.

Reviewed by:	bz
Sponsored by:	The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D56441

This is a global variable used to track the state of the system, like
booting, running, halting and so on.

This variable is based on the `enum system_states` enumeration.

For now, always set `system_state` to `SYSTEM_RUNNING`.

The amdgpu DRM driver started to use this in Linux 6.12.x.

Reviewed by:	emaste
Sponsored by:	The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D56575

They are no-ops on FreeBSD.

While here, move the already defined `might_sleep*()` macros from
<linux/wait.h> to <linux/kernel.h> where they belong.

The DRM generic code started to use `might_fault()` in Linux 6.12.

Reviewed by:	bz
Sponsored by:	The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D56434

New Linux v7.0 drivers include hex.h.  Rather than adding a dummy
header, migrate the kernel.h hex2bin() into hex.h, where it belongs.
Care needs to be taken as the _h2b() helper function is still used by
other bits in kernel.h.

Sponsored by:	The FreeBSD Foundation
MFC after:	3 days
Reviewed by:	emaste, dumbbell
Differential Revision: https://reviews.freebsd.org/D56391

This matches the declaration on Linux.

Reviewed by:	bz, emaste
Sponsored by:	The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D55730

MFC after:	1 week

This include prevents usage of any kernel.h helpers in sched.h and
all of dependencies. Linux does not have it too.
Fix building of kernel and drm-kmod after than.

Sponsored by:	Serenity CyberSecurity, LLC
MFC after:	1 week
Reviewed by:	manu, bz
Differential Revision:	https://reviews.freebsd.org/D45692

from linux/kernel.h to match Linux and
allow direct linux/kstrtox.h inclusion.

Sponsored by:	Serenity Cyber Security, LLC
MFC after:	1 week
Reviewed by:	bz
Differential Revision:	https://reviews.freebsd.org/D45454

To match Linux and allow direct linux/math.h inclusion.

Sponsored by:	Serenity Cyber Security, LLC
MFC after:	1 week
Reviewed by:	bz
Differential Revision:	https://reviews.freebsd.org/D45452