tools include UAPI: Update linux/mount.h copy

To pick the changes from:

  dab741e0e0 ("Add a "nosymfollow" mount option.")

That ends up adding support for the new MS_NOSYMFOLLOW mount flag:

  $ tools/perf/trace/beauty/mount_flags.sh > before
  $ cp include/uapi/linux/mount.h tools/include/uapi/linux/mount.h
  $ tools/perf/trace/beauty/mount_flags.sh > after
  $ diff -u before after
  --- before	2020-11-03 08:51:28.117997454 -0300
  +++ after	2020-11-03 08:51:38.992218869 -0300
  @@ -7,6 +7,7 @@
   	[32 ? (ilog2(32) + 1) : 0] = "REMOUNT",
   	[64 ? (ilog2(64) + 1) : 0] = "MANDLOCK",
   	[128 ? (ilog2(128) + 1) : 0] = "DIRSYNC",
  +	[256 ? (ilog2(256) + 1) : 0] = "NOSYMFOLLOW",
   	[1024 ? (ilog2(1024) + 1) : 0] = "NOATIME",
   	[2048 ? (ilog2(2048) + 1) : 0] = "NODIRATIME",
   	[4096 ? (ilog2(4096) + 1) : 0] = "BIND",
  $

So now one can use it in --filter expressions for tracepoints.

This silences this perf build warnings:

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

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mattias Nissler <mnissler@chromium.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/include/uapi/linux/mount.h

@@ -16,6 +16,7 @@
 #define MS_REMOUNT	32	/* Alter flags of a mounted FS */
 #define MS_MANDLOCK	64	/* Allow mandatory locks on an FS */
 #define MS_DIRSYNC	128	/* Directory modifications are synchronous */
+#define MS_NOSYMFOLLOW	256	/* Do not follow symlinks */
 #define MS_NOATIME	1024	/* Do not update access times. */
 #define MS_NODIRATIME	2048	/* Do not update directory access times */
 #define MS_BIND		4096