ggml-qnn: fix minor issue in test-backend-ops.cpp

Author: zhouwg

tests/test-backend-ops.cpp

@@ -4471,7 +4471,11 @@ int main(int argc, char ** argv) {
             continue;
         }
 
+#ifdef GGML_USE_QNN
+        ggml_backend_t backend = ggml_backend_dev_init(dev, reinterpret_cast<const char *>(i));
+#else
         ggml_backend_t backend = ggml_backend_dev_init(dev, NULL);
+#endif
         GGML_ASSERT(backend != NULL);
 
         ggml_backend_reg_t reg = ggml_backend_dev_backend_reg(dev);