tracing: Add a seq_buf_clear() helper and clear len and readpos in init

Add a helper function seq_buf_clear() that resets the len and readpos
fields of a seq_buf. Currently it is only used in the seq_buf_init()
but will be used later when updating the seq_file code.

Link: http://lkml.kernel.org/r/[e-mail]

Tested-by: Jiri Kosina <[e-mail]>
Acked-by: Jiri Kosina <[e-mail]>
Reviewed-by: Petr Mladek <[e-mail]>
Signed-off-by: Steven Rostedt <[e-mail]>

include/linux/seq_buf.h

···
 	loff_t			readpos;
 };
 
+static inline void seq_buf_clear(struct seq_buf *s)
+{
+	s->len = 0;
+	s->readpos = 0;
+}
+
 static inline void
 seq_buf_init(struct seq_buf *s, unsigned char *buf, unsigned int size)
 {
 	s->buffer = buf;
 	s->size = size;
-	s->len = 0;
-	s->readpos = 0;
+	seq_buf_clear(s);
 }
 
 /*