headers_check: special case seqbuf_dump()

headers_check: special case seqbuf_dump()

"make headers_check" warns about soundcard.h for (at least) five years
now:
    [...]/usr/include/linux/soundcard.h:1054: userspace cannot reference function or variable defined in the kernel

We're apparently stuck with providing OSSlib-3.8 compatibility, so let's
special case this declaration just to silence it.

Notes:

0) Support for OSSlib post 3.8 was already removed in commit 43a990765a
   ("sound: Remove OSSlib stuff from linux/soundcard.h").  Five years have
   passed since that commit: do people still care about OSSlib-3.8?  If
   not, quite a bit of code could be remove from soundcard.h (and probably
   ultrasound.h).

2) By the way, what is actually meant by:
    It is no longer possible to actually link against OSSlib with this
    header, but we still provide these macros for programs using them.

Doesn't that mean compatibility to OSSlib isn't even useful?

3) Anyhow, a previous discussion soundcard.h, which led to that commit,
   starts at https://lkml.org/lkml/2009/1/20/349 .

4) And, yes, I sneaked in a whitespace fix.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Cc: Takashi Iwai <tiwai@suse.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: Michal Marek <mmarek@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>