tools headers asm: Sync fls headers header with the kernel sources

tools headers asm: Sync fls headers header with the kernel sources

To pick the changes in:

  6606c8c7e8188656 ("bitops: Add __attribute_const__ to generic ffs()-family implementations")

This addresses these tools build warnings:

  Warning: Kernel ABI header differences:
    diff -u tools/include/asm-generic/bitops/__fls.h include/asm-generic/bitops/__fls.h
    diff -u tools/include/asm-generic/bitops/fls.h include/asm-generic/bitops/fls.h
    diff -u tools/include/asm-generic/bitops/fls64.h include/asm-generic/bitops/fls64.h

Please see tools/include/uapi/README for further details.

Cc: Kees Cook <kees@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>