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

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

To pick up changes from:

  78f0e33cd6c939a5 ("fs/namespace: correctly handle errors returned by grab_requested_mnt_ns")

This should be used to beautify mount syscall arguments and it addresses
these tools/perf build warnings:

  Warning: Kernel ABI header differences:
    diff -u tools/perf/trace/beauty/include/uapi/linux/mount.h include/uapi/linux/mount.h

Please see tools/include/uapi/README.

Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>