This reverts commit 602249f033d146d9c731d8b1cb4b2e0899c61ad9.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week

Implement devm_kmemdup_array() using devm_kmemdup() in order to
prepare for Linux v7.0 based drivers.

Sponsored by:	The FreeBSD Foundation
MFC after:	3 days
Reviewed by:	dumbbell
Differential Revision: https://reviews.freebsd.org/D56396

Drivers in Linux v7.0 seem to have changed to the new allocation
macros using a sweep.  Add the ones I encountered with wireless
drivers so far.  They all take an optional argument for a gfp_t,
which default_gfp() deals with.

The plural version "objs" takes an extra nitems argument in addition
to the size.  We use size_mul() to possibly detect overflows.

The "flex" version uses an extra variable to track the variable sized
array allocations and if supported by the compiler will use
__builtin_counted_by_ref() to properly track bounds.

Sponsored by:	The FreeBSD Foundation
MFC after:	3 days
Reviewed by:	dumbbell
Differential Revision: https://reviews.freebsd.org/D56395

overflow.h was imported directly from Linux in 3208d4ad2b8320a.
Update the file to the newer version as needed for v7.0 driver updates.

Sponsored by:	The FreeBSD Foundation
MFC after:	3 days
Obtained from:	git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
		028ef9c96e96197026887c0f092424679298aae8 (tag: v7.0)
Reviewed by:	emaste, dumbbell
Differential Revision: https://reviews.freebsd.org/D56394

__flex_counter() is used by overflow.h and needed for "flex allocations".
It is either a void * typed 0 (NULL) (like this for _Generic checks),
or uses __builtin_counted_by_ref.

The latter was added to gcc and llvm fairly recently and while for gcc
the __has_builtin() check suffices, clang had parts broken until recently
so needs an extra check for the next major version.  The fixed hash is
currently not part of any tag to use, so we play it save (and hope 23
will have it).  It will be a while until we will see the builting to be
used but at least we will be prepared for it.  See inline comments for
the commit hashes and versions which added the feature.

Sponsored by:	The FreeBSD Foundation
MFC after:	3 days
Reviewed by:	dumbbell
Differential Revision: https://reviews.freebsd.org/D56393

Various new allocation macros can take an optional gfp_t argument.
If the argument is not given we need to set the GFP_KERNEL default.
While this is only internally used and I initialy called it differently,
should this spread elsewhere having the same name as in Linux will be
good.

Sponsored by:	The FreeBSD Foundaton
MFC after:	3 days
Reviewed by:	dumbbell
Differential Revision: https://reviews.freebsd.org/D56392

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

Add the struct for VHT information and flags for the known and flag
field as documented on radiotap.org.  iwlwifi has started filling in
these details.

While here, add Copyright information for all the additions in the
last years.

Sponsored by:	The FreeBSD Foundation
MFC after:	3 days