Updated sbx connections

After converting to the 381pin package the connection from the rekclk
receiver to the PCIe core was lost. This change reconnects it.
Corrected compilation errors.

1) The inline comments in the .LPF file had to be removed.
2) The oscillator clock (clk) routed to A19 failed compilation. The
internal logic was changed to run off the 125MHz clock recovered from
the PCI Express interface.