This allows us to convert aucom to just another com attachment, and cleanup
some code in the com_arbus.c.
Additionally, we use a common com_cleanup routine rather than having a
zillion copies of it in the attachment points.
This has been tested on a number architectures, and it has been shown to get
close to comparable performance when COM_REGMAP is defined, and comparable
when it is not defined.
Approved by core@. Fixes PR port-evbmips/32362.
PowerPC and provides a PCI-host bridge, interrupt controller, two com ports,
two IIC ports, a timer, and a DRAM controller.
The driver supports PCI, interrupts and com ports.
martin