relay: remove redundant assignment to pointer buf

Pointer buf is being assigned a value that is not being read, buf is being
re-assigned in the next starement.  The assignment is redundant and can be
removed.

Cleans up clang scan build warning:
kernel/relay.c:443:8: warning: Although the value stored to 'buf' is
used in the enclosing expression, the value is never actually read
from 'buf' [deadcode.DeadStores]

Link: https://lkml.kernel.org/r/20220508212152.58753-1-colin.i.king@gmail.comSigned-off-by: NColin Ian King <colin.i.king@gmail.com>
Reviewed-by: NJens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

kernel/relay.c

@@ -440,7 +440,7 @@ int relay_prepare_cpu(unsigned int cpu)
 
 	mutex_lock(&relay_channels_mutex);
 	list_for_each_entry(chan, &relay_channels, list) {
-		if ((buf = *per_cpu_ptr(chan->buf, cpu)))
+		if (*per_cpu_ptr(chan->buf, cpu))
 			continue;
 		buf = relay_open_buf(chan, cpu);
 		if (!buf) {