fixup(BSS2): stablize BSS-2 operation

This introduces stabilizing fixes to support error counter overflows (for long-lasting experiments), lowers JTAG operation frequency to robustify readout of, e.g., chip version information.

@elmath I'm sorry… that's the third MR for BSS-2 software in this release cycle — we encountered more instability (than usual) which required some fix ups (some people try to run >5-hour experiments w/o resetting the host-FPGA connection in between… crazy! )

merged