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

To pick up changes from:

  78f0e33 ("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>

Author: namhyung

tools/perf/trace/beauty/include/uapi/linux/mount.h

@@ -197,7 +197,7 @@ struct statmount {
  */
 struct mnt_id_req {
 	__u32 size;
-	__u32 spare;
+	__u32 mnt_ns_fd;
 	__u64 mnt_id;
 	__u64 param;
 	__u64 mnt_ns_id;