ds1620: single_open() leak

Cc: [e-mail]
Signed-off-by: Al Viro <[e-mail]>

drivers/char/ds1620.c

···
 	.open		= ds1620_proc_therm_open,
 	.read		= seq_read,
 	.llseek		= seq_lseek,
-	.release	= seq_release,
+	.release	= single_release,
 };
 #endif