kernel: relay: remove unnecessary NULL values from relay_open_buf

buf is assigned first, so it does not need to initialize the assignment.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Li kunyu <[e-mail]>
Reviewed-by: Andrew Morton <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

kernel/relay.c

···
  */
 static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
 {
- 	struct rchan_buf *buf = NULL;
+	struct rchan_buf *buf;
 	struct dentry *dentry;
 
  	if (chan->is_global)