[GPU] Fixed uninit axis field in pooling prim (#9598)

src/plugins/intel_gpu/include/intel_gpu/primitives/pooling.hpp

@@ -231,7 +231,7 @@ struct pooling : public primitive_base<pooling> {
     /// @brief Defines a shift, relative to the end of padding shape.
     tensor pad_end;
     /// @brief first dimension of input that should be used to calculate the upper bound of index output
-    int64_t axis;
+    int64_t axis = 0;
     /// @brief type of index output
     data_types index_element_type = data_types::i32;
     bool maxPoolOpset8Features{false};