Uart in picorv32 example


I got the picorv32 example running and added back the uart console code and the PicoSoc banner. I am using a USB uart device on pins 1 and 2. (Well just pin 1 for console output).

reg_uart_clkdiv is set to 139 for the 16Mhz clock (16M / 115200).

It would be nice if the usb connector could be used for the uart, but this would presumably need a copy of most of the bootloader and there would be insufficient resources to add all that to picosoc.

I have also produced a simple Hello World uart example without using picosoc, but using the simpleuart module from picosoc.