misc: mei: client.c: fix problem of return '-EOVERFLOW' in mei_cl_write

Clang static analyzer complains that value stored to 'rets' is never
read.Let 'buf_len = -EOVERFLOW' to make sure we can return '-EOVERFLOW'.

Fixes: 8c8d964 ("mei: move hbuf_depth from the mei device to the hw modules")
Signed-off-by: Su Hui <suhui@nfschina.com>
Link: https://lore.kernel.org/r/20231120095523.178385-2-suhui@nfschina.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/mei/client.c

@@ -2032,7 +2032,7 @@ ssize_t mei_cl_write(struct mei_cl *cl, struct mei_cl_cb *cb, unsigned long time
 
 	hbuf_slots = mei_hbuf_empty_slots(dev);
 	if (hbuf_slots < 0) {
-		rets = -EOVERFLOW;
+		buf_len = -EOVERFLOW;
 		goto out;
 	}