The GPU on the laptop's motherboard has the GPU soldered onto the board, so the only way to change your GPU is to change the entire laptop.
Even if you found a motherboard that had the GPU you'r looking for while retaining your old processor, you won't be able to align the I/O ports on the edge of the case since each SKU will have varying placements for their ports.
In short, no, you can't upgrade the GPU on your Dell Inspiron 5520 laptop.