No, there is no capability within HDL Coder to generate Simulink from HDL; the tool works exclusively in the other direction.
If you need to import VHDL into a larger design, you can use HDL Coder's Black Box feature to include handwritten HDL code into a larger set of generated HDL code. You could also use HDL Verifier to cosimulate hand-written HDL code in a Simulink design.
