Fix: Improved null test to run your c script simulation

[M-shahid-saeed]

While performing C-script simulations for the cl_dram_hbm_dma example, I encountered an issue where the simulation environment was not correctly synchronizing with the software-side execution in test_null.sv.

Since FPGA resources are costly, verifying the C-runtime logic through simulation before hardware deployment is critical. This PR adds specific helper functions/logic to test_null.sv to:

Ensure the C-script triggers the hardware simulation correctly.

Provide better visibility into software-to-hardware handshakes during null tests.

Prevent simulation hangs when running the specific HBM/DRAM DMA software stack.

Verified on the HDK simulation environment.

[mjthimm]

Hi @M-shahid-saeed,

We're happy to accept this PR once the following changes are made:

• fix the indentation on the include statement
• fix the indentation on the initialize_ddr() and deselect_cl_tst_hw() function calls

Best,
Max