Add HIDL_FETCH_IScheduleTest declaration

Fix the bug that makes the registerAsServer fail.
sp<IScheduleTest> server =
	IScheduleTest::getService(serviceName, true);
status_t status = server->registerAsService(serviceName);

Bug:38099333
Test: oc-dev on pixel sailfish with a vts test case
  "libhwbinder_latency -i 1"
Change-Id: I892835a25ef7df56a6424da41c0fc477b3a532d8

tests/libhwbinder/1.0/default/ScheduleTest.h

@@ -31,6 +31,8 @@ struct ScheduleTest : public IScheduleTest {
     // Methods from ::android::hidl::base::V1_0::IBase follow.
 };
 
+extern "C" IScheduleTest* HIDL_FETCH_IScheduleTest(const char* name);
+
 }  // namespace implementation
 }  // namespace V1_0
 }  // namespace libhwbinder