Software Driver for custom AXI-stream IP in Xilinx SDK
In that case, you have to write those driver APIs yourself. That's what I have done in the past. Then you have to mention the path of your newly created custom driver files in the driver repositories in SDK and reload and rebuild your BSP. 

Note that, it is not mandatory for the drivers to have the same format as Xilinx's AXI IP drivers. In fact, you can live with those two functions that Vivado has given you. Only that's enough actually in most cases to access your IP as it is just a memory mapped peripheral to which you want to either read or write.