Add tests for bsg_two_fifo

[OroArmor]

The change in bsg_two_fifo.sv might not be necessary, however I found that without it the head_r and tail_r pointers would no longer be equal, causing an invalid state for the FIFO.

basejump_stl/bsg_dataflow/bsg_two_fifo.sv

Line 74 in 9322a57

assign enq_i = v_i & (full_r & deq_i | ~full_r);

I am also curious how to make the allow_enq_deq_on_full_p in bsg_two_fifo_wrapper potentially.sv be something that can be properly parameterized, allowing both the normal and passthrough configurations to be tested.