It is possible to control the generated function prototype of an Atomic Subsystem. Please use the options in the Code Generation pane in the Atomic Subsystem's block parameters dialog box. To change the name, you would need to set "Function name options" to "User specified" and then enter the desired function name. There are additional options to control the function signature such as the ability to allow arguments. The following link will provide more information on these:
Please note that parameters on the Code Generation tab require a Simulink Coder or Embedded Coder license.
