[patch] relay: check array offset before using it

[Dan Carpenter]

Smatch complains that we started using the array offset before we
checked that it was valid.

Fixes: 017c59c042d0 ('relay: Use per CPU constructs for the relay channel 
buffer pointers')
Signed-off-by: Dan Carpenter <dan.carpen...@oracle.com>

diff --git a/kernel/relay.c b/kernel/relay.c
index da79a10..8f18d31 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -809,11 +809,11 @@ void relay_subbufs_consumed(struct rchan *chan,
 {
        struct rchan_buf *buf;
 
-       if (!chan)
+       if (!chan || cpu >= NR_CPUS)
                return;
 
        buf = *per_cpu_ptr(chan->buf, cpu);
-       if (cpu >= NR_CPUS || !buf || subbufs_consumed > chan->n_subbufs)
+       if (!buf || subbufs_consumed > chan->n_subbufs)
                return;
 
        if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)