Documentation: update seq_file

Update descriptions of seq_path() and seq_path_root():
starting with commit v3.2-rc4-1-g02125a8, seq_path_root() no longer
changes the value of root;
starting with commit v3.2-rc7-104-g8c9379e, some arguments of seq_path()
and seq_path_root() are const.

Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Acked-by: Rob Landley <rob@landley.net>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/filesystems/seq_file.txt

@@ -194,16 +194,16 @@ which is in the string esc will be represented in octal form in the output.
 
 There are also a pair of functions for printing filenames:
 
-	int seq_path(struct seq_file *m, struct path *path, char *esc);
-	int seq_path_root(struct seq_file *m, struct path *path,
-			  struct path *root, char *esc)
+	int seq_path(struct seq_file *m, const struct path *path,
+		     const char *esc);
+	int seq_path_root(struct seq_file *m, const struct path *path,
+			  const struct path *root, const char *esc)
 
 Here, path indicates the file of interest, and esc is a set of characters
 which should be escaped in the output.  A call to seq_path() will output
 the path relative to the current process's filesystem root.  If a different
-root is desired, it can be used with seq_path_root().  Note that, if it
-turns out that path cannot be reached from root, the value of root will be
-changed in seq_file_root() to a root which *does* work.
+root is desired, it can be used with seq_path_root().  If it turns out that
+path cannot be reached from root, seq_path_root() returns SEQ_SKIP.
 
 A function producing complicated output may want to check
 	bool seq_has_overflowed(struct seq_file *m);