Licenses for special operations

In this file, we list the operations with other licenses instead of Apache 2.0. Users should be careful about adopting these operations in any commercial matters.

Operation	Files	License
upfirdn2d	mmcv/ops/csrc/pytorch/cuda/upfirdn2d_kernel.cu	NVIDIA License
fused_leaky_relu	mmcv/ops/csrc/pytorch/cuda/fused_bias_leakyrelu_cuda.cu	NVIDIA License