FSL/PLB/NPI were supported and documented in earlier versions (such as 2012.2).
However Vivado HLS does not officially support it now.
Although it still may work, it is not documented.
Users are advised to use AXI4-Stream interface direct connection with the MicroBlaze.
In Xilinx User Guide UG081 they are referred as M0_AXIS.. M15_AXIS for the masters interfaces and the corresponding S0_AXIS.. S15_AXIS for the response/slave interface.