kfdtest: Add return statement for ReadSMIEventThread

This didn't return anything, so add a "return 0" at the end, since the
function expects to return an int value

Change-Id: I17c398e431b2ce4571e6ca4abe6d567f110ea2a7

tests/kfdtest/src/KFDSVMRangeTest.cpp

@@ -1445,6 +1445,7 @@ unsigned int ReadSMIEventThread(void* p) {
     EXPECT_EQ(pid, getpid());
     EXPECT_EQ(trigger, HSA_MIGRATE_TRIGGER_PREFETCH);
     close(fd);
+    return 0;
 }
 
 TEST_F(KFDSVMRangeTest, HMMProfilingEvent) {