tools headers UAPI: Sync linux/prctl.h with the kernel sources

To pick the changes in:

  9e4ab6c8

 ("arm64/sme: Implement vector length configuration prctl()s")

That don't result in any changes in tooling:

  $ tools/perf/trace/beauty/prctl_option.sh > before
  $ cp include/uapi/linux/prctl.h tools/include/uapi/linux/prctl.h
  $ tools/perf/trace/beauty/prctl_option.sh > after
  $ diff -u before after
  $

Just silences this perf tools build warning:

  Warning: Kernel ABI header at 'tools/include/uapi/linux/prctl.h' differs from latest version at 'include/uapi/linux/prctl.h'
  diff -u tools/include/uapi/linux/prctl.h include/uapi/linux/prctl.h

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Link: http://lore.kernel.org/lkml/Yq81we+XFOqlBWyu@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>