ACPI: watchdog: Replace open coded variant of resource_union()

Since we have resource_union() helper, let's utilize it here.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Tested-by: Hanjun Guo <guohanjun@huawei.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpi_watchdog.c

@@ -151,11 +151,7 @@ void __init acpi_watchdog_init(void)
 		found = false;
 		resource_list_for_each_entry(rentry, &resource_list) {
 			if (rentry->res->flags == res.flags &&
-			    resource_overlaps(rentry->res, &res)) {
-				if (res.start < rentry->res->start)
-					rentry->res->start = res.start;
-				if (res.end > rentry->res->end)
-					rentry->res->end = res.end;
+			    resource_union(rentry->res, &res, rentry->res)) {
 				found = true;
 				break;
 			}