perf beauty: Switch from using uapi/linux/fs.h to uapi/linux/mount.h

As now we'll update our fs.h copy and what tools/perf/trace/beauty/mount_flags.sh
needs just got moved to mount.h, use that instead.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-ls19h376xukeouxrw9dswkcn@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>