tracing: Convert seq_buf fields to be like seq_file fields

In facilitating the conversion of seq_file to use seq_buf,
have the seq_buf fields match the types used by seq_file.

Link: http://lkml.kernel.org/r/20141104160222.195301024@goodmis.org

Tested-by: Jiri Kosina <jkosina@suse.cz>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Reviewed-by: Petr Mladek <pmladek@suse.cz>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

include/linux/seq_buf.h

@@ -16,10 +16,10 @@
  * @readpos:	The next position to read in the buffer.
  */
 struct seq_buf {
-	unsigned char		*buffer;
-	unsigned int		size;
-	unsigned int		len;
-	unsigned int		readpos;
+	char			*buffer;
+	size_t			size;
+	size_t			len;
+	loff_t			readpos;
 };
 
 static inline void