Merge pull request #28634 from abhishek-gola:flops_addition

Added getFLOPS support in new DNN engine #28634

closes: https://github.com/opencv/opencv/issues/26199

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake

modules/dnn/perf/perf_net.cpp

@@ -65,9 +65,7 @@ public:
         size_t weightsMemory = 0, blobsMemory = 0;
         net.getMemoryConsumption(netMatShapes, netMatTypes, weightsMemory, blobsMemory);
         int64 flops = net.getFLOPS(netMatShapes, netMatTypes);
-        // [TODO] implement getFLOPS in the new engine
-        // Issue: https://github.com/opencv/opencv/issues/26199
-        CV_Assert(flops > 0 || net.getMainGraph());
+        CV_Assert(flops > 0);
         std::cout << "Memory consumption:" << std::endl;
         std::cout << "    Weights(parameters): " << divUp(weightsMemory, 1u<<20) << " Mb" << std::endl;
         std::cout << "    Blobs: " << divUp(blobsMemory, 1u<<20) << " Mb" << std::endl;