resource: provide meaningful MODULE_LICENSE() in test suite

modpost complains that module has no licence provided.
Provide it via meaningful MODULE_LICENSE().

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

kernel/resource_kunit.c

@@ -148,3 +148,5 @@ static struct kunit_suite resource_test_suite = {
 	.test_cases = resource_test_cases,
 };
 kunit_test_suite(resource_test_suite);
+
+MODULE_LICENSE("GPL");