Add ARM32 UART Serial Controller

[tgiphil]

Implement a simple serial controller for ARM32.

And complete the PlatformPlug.SerialPlug plug interface:

https://github.com/mosa/MOSA-Project/blob/master/Source/Mosa.Kernel.BareMetal.ARM32/PlatformPlug.cs#L116

This is the first step to integrating the baremetal kernel.

[tgiphil]

Might be helpful:

https://github.com/umanovskis/baremetal-arm/blob/master/doc/06_uart.md

[tgiphil]

And this shorter version:

https://github.com/ronalterde/raspberrypi-zero/blob/master/uart01/notmain.c