w1: use correct lock on error in w1_seq_show()

I noticed there was a problem here because Smatch complained:

	drivers/w1/slaves/w1_therm.c:416 w1_seq_show() warn:
	inconsistent returns 'mutex:&sl->master->mutex'.
	  Locked on:   line 416
	  Unlocked on: line 413

The problem is that we lock ->mutex but we unlock ->bus_mutex on error.
David Fries says that ->bus_mutex is correct and ->mutex is incorrect.

Fixes: d9411e57 ('w1: Add support for DS28EA00 sequence to w1-therm')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/w1/slaves/w1_therm.c

@@ -355,7 +355,7 @@ static ssize_t w1_seq_show(struct device *device,
 	struct w1_reg_num *reg_num;
 	int seq = 0;
 
-	mutex_lock(&sl->master->mutex);
+	mutex_lock(&sl->master->bus_mutex);
 	/* Place all devices in CHAIN state */
 	if (w1_reset_bus(sl->master))
 		goto error;
@@ -407,7 +407,7 @@ static ssize_t w1_seq_show(struct device *device,
 	ack = w1_read_8(sl->master);
 	if (ack != W1_42_SUCCESS_CONFIRM_BYTE)
 		goto error;
-	mutex_unlock(&sl->master->mutex);
+	mutex_unlock(&sl->master->bus_mutex);
 
 	c -= snprintf(buf + PAGE_SIZE - c, c, "%d\n", seq);
 	return PAGE_SIZE - c;