missing null termination in one wire uevent

Need to null terminate environment.  Found by inspection while looking for
similar problems to platform uevent bug

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Acked-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/w1/w1.c

@@ -431,6 +431,7 @@ static int w1_uevent(struct device *dev, char **envp, int num_envp,
 	err = add_uevent_var(envp, num_envp, &cur_index, buffer, buffer_size,
 			&cur_len, "W1_SLAVE_ID=%024LX",
 			(unsigned long long)sl->reg_num.id);
+	envp[cur_index] = NULL;
 	if (err)
 		return err;