No functional change:
- Rename function for consistency.
- Add prototypes.
- KNF.

PUCCN improvements:
- Fix a bug that the puc cn mechanism doesn't use the UART's frequency
in pucdata.c's table.

- Add a new option PUC_CNAUTO. If this option is set, consinit() in
x86/x86/consinit.c checks puc com device to use it as console.
Without this option, the behavior is the same as before.

- Add a new config parameter PUC_CNBUS. The old code scans bus #0 only.
If PUC_CNBUS is set, the specified number's bus will be scanned.

- Rename comcnprobe() to puc_cnprobe() to make it clear.

- Rename comcninit() to puc_cninit() to make it clear.

- Add code for a device that a device's com register is MMIO (#if0 ed).

Allow console on com_puc without a compile-time option so that PC servers
can become headless after the first reboot (sadly, e.g. Intel AMT presents
as a com_puc, but doesn't appear in the BIOS serial port table, so you need
a keyboard and monitor to install and set the installboot parameters first).

Fix com_puc console on devices with offset BAR's.

branches: 1.4.110; 1.4.120; 1.4.126; 1.4.134;
merge ktrace-lwp.

function prototype must not have variable name

branches: 1.2.24;
Change $Id: to $NetBSD$

branches: 1.1.2;
Add code to allow the PCI com serial ports to be used as the system
console. This is not enabled by default, and is turned on with
options PUCCN. Done by castor@netbsd.org.