added testbench for rdma_packetiser_assemble_header

applications/rdma_demo/libraries/rdma_packetiser/hdllib.cfg

...a_packetiser/src/vhdl/rdma_packetiser_assemble_header.vhd

...ibraries/rdma_packetiser/src/vhdl/rdma_packetiser_pkg.vhd

...packetiser/tb/vhdl/tb_rdma_packetiser_assemble_header.vhd

...ketiser/tb/vhdl/tb_tb_rdma_packetiser_assemble_header.vhd