rtc: rs5c372: fix buffer size

Match the buffer size to the amount of initialized values.  Before, it was
one too big and thus destroyed the neighbouring register causing the clock
to run at false speeds.
Reported-by: Andre van Rooyen <a.v.rooyen@sercom.nl>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/rtc-rs5c372.c

@@ -207,7 +207,7 @@ static int rs5c372_get_datetime(struct i2c_client *client, struct rtc_time *tm)
 static int rs5c372_set_datetime(struct i2c_client *client, struct rtc_time *tm)
 {
 	struct rs5c372	*rs5c = i2c_get_clientdata(client);
-	unsigned char	buf[8];
+	unsigned char	buf[7];
 	int		addr;
 
 	dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d "