Probably leftover from the time we introducd the check-headers.sh script.

Committer testing:

Remove the 'rseq' syscall from tools/perf/arch/x86/entry/syscalls/syscall_64.tbl
to fake a diff:

make: Entering directory '/home/acme/git/perf/tools/perf'
  BUILD:   Doing 'make -j4' parallel build
Warning: Kernel ABI header at 'tools/perf/arch/x86/entry/syscalls/syscall_64.tbl' differs from latest version at 'arch/x86/entry/syscalls/syscall_64.tbl'
diff -u tools/perf/arch/x86/entry/syscalls/syscall_64.tbl arch/x86/entry/syscalls/syscall_64.tbl
  CC       /tmp/build/perf/util/syscalltbl.o
  INSTALL  trace_plugins
<SNIP>
  $ diff -u tools/perf/arch/x86/entry/syscalls/syscall_64.tbl arch/x86/entry/syscalls/syscall_64.tbl
  --- tools/perf/arch/x86/entry/syscalls/syscall_64.tbl	2018-08-13 15:49:50.896585176 -0300
  +++ arch/x86/entry/syscalls/syscall_64.tbl	2018-07-20 12:04:04.536858304 -0300
  @@ -342,6 +342,7 @@
   331	common	pkey_free		__x64_sys_pkey_free
   332	common	statx			__x64_sys_statx
   333	common	io_pgetevents		__x64_sys_io_pgetevents
  +334	common	rseq			__x64_sys_rseq

  #
  # x32-specific system call numbers start at 512 to avoid cache impact
  $
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Kapshuk <alexander.kapshuk@gmail.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180813111504.3568-2-jolsa@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>