sim: Update UARTs to use the upstream OpenTitan UART

This stops us from using the "OpenTitan2" UART that we have in shodan
infrastructure in deference to the real one in the upstream Renode
code, which matches upstream OpenTitan and all it's register warts.

Bug: 228243751
Change-Id: I91bf4dc23ad38ff90f4043548d986abb85f189ce
1 file changed