Added debug bridge to the PCIe configuration space of endpoint 0, so an ILA...
Use BUFGCTRL to switch between clk40_xtal and clk_ttc_40, instead of secondary inputs of MMCM. This switched clock is directly used as a Si5345 reference, so the MMCM is bypassed, reducing the jitter on the Si5345 input.
Closes FLX-2148