Unfortunately, we do not support flashing the board from Simulink using P&E Multilink or JLink.
Instead of using the OpenSDA you can use the RappId Bootloader alternative. This implies flashing once the bootloader using Jtag and then using the Serial for deploying the generated code directly from Simulink on the board.
Since the compiling process generates the .elf file, another option would be to flash the generated .elf file using S32DS after the code has been generated and built.
Hope this helps,