svm: finish all queues in svm_pointer_passing

The `svm_pointer_passing` has unflushed buffer unmap commands queued,
which a runtime might process after the `clSVMFree` calls at the end of
the test (through implicit flushing when destroying the queues at e.g.
program exit handlers).

This is only an issue when running the test with multiple devices

Author: karolherbst

test_conformance/SVM/test_pointer_passing.cpp

@@ -127,10 +127,10 @@ REGISTER_TEST(svm_pointer_passing)
                     return -1;
                 }
             }
-        }
 
-        error = clFinish(cmdq);
-        test_error(error, "clFinish failed");
+            error = clFinish(cmdq);
+            test_error(error, "clFinish failed");
+        }
     }