rtc: sysfs: Bail out earlier if no new groups provided

When there is no new groups provided, no need to reallocate memory,
copy the old ones and free them in order to do nothing. Do nothing
instead.

Signed-off-by: Andy Shevchenko <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexandre Belloni <[e-mail]>

drivers/rtc/sysfs.c

···
 	size_t old_cnt = 0, add_cnt = 0, new_cnt;
 	const struct attribute_group **groups, **old;
 
-	if (!grps)
+	if (grps) {
+		for (groups = grps; *groups; groups++)
+			add_cnt++;
+		/* No need to modify current groups if nothing new is provided */
+		if (add_cnt == 0)
+			return 0;
+	} else {
 		return -EINVAL;
+	}
 
 	groups = rtc->dev.groups;
 	if (groups)
 		for (; *groups; groups++)
 			old_cnt++;
-
-	for (groups = grps; *groups; groups++)
-		add_cnt++;
 
 	new_cnt = old_cnt + add_cnt + 1;
 	groups = devm_kcalloc(&rtc->dev, new_cnt, sizeof(*groups), GFP_KERNEL);