Revert "anon_inode: set S_IFREG on the anon_inode"

This reverts commit a7cf4145bb86aaf85d4d4d29a69b50b688e2e49d.

fs/anon_inodes.c

···
 	 * that it already _is_ on the dirty list.
 	 */
 	inode->i_state = I_DIRTY;
-	inode->i_mode = S_IFREG | S_IRUSR | S_IWUSR;
+	inode->i_mode = S_IRUSR | S_IWUSR;
 	inode->i_uid = current_fsuid();
 	inode->i_gid = current_fsgid();
 	inode->i_flags |= S_PRIVATE;