tools/headers: Regenerate stddef.h to fix BPF selftests

tools/headers: Regenerate stddef.h to fix BPF selftests

With commit dacbfc167808 ("crypto: af_alg - Annotate struct af_alg_iv
with __counted_by"), two selftests, test_tag and crypto_sanity, now
indirectly rely on the __counted_by macro. On systems with commit
dacbfc167808 in the installed UAPI headers, the selftests build fails
with:

  In file included from tools/testing/selftests/bpf/prog_tests/crypto_sanity.c:7:
  /usr/include/linux/if_alg.h:45:22: error: expected ‘:’, ‘,’, ‘;’, ‘}’ or ‘__attribute__’ before ‘__counted_by’
     45 |         __u8    iv[] __counted_by(ivlen);
        |                      ^~~~~~~~~~~~

This patch fixes it by regenerating stddef.h in tools/include using the
instructions from commit a778f5d46b62 ("tools/headers: Pull in stddef.h
to uapi to fix BPF selftests build in CI").

Fixes: dacbfc167808 ("crypto: af_alg - Annotate struct af_alg_iv with __counted_by")
Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Tested-by: Ihor Solodrai <ihor.solodrai@linux.dev>
Link: https://lore.kernel.org/r/8da8ef16055aa452d940668ed5359ce54adc6b0b.1777715500.git.paul.chaignon@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>