[TSilk] modifications
- "DIOT (Distributed I/O Tier) System Board" change to "Distributed I/O Tier System Board" and move it maybe to the FMC area so that it is not covered by the FPGA heatsink? Unless you find a better place. Put it also on the back silkscreen.
- near J4 add text "WR ABSCAL"
- near J8 add text "WR PPS"
- add description to PB2 (PS POR) and PB3 (PS SRST)