Refactor and cleanup sio (uPD7201) drivers.

- remove confusing syscn*() functions (and its header) and prepare
explicit siottycninit(), siottycnget() and siottycnput() functions
- use exported struct consdev and cn_tab to initialize siotty console
- enable and handle E/S interrupts to make BREAK signal detected properly
- make CSR (status regsiters) access functions inline static
- make single byte read/write (i.e. cnputc() and cngetc()) functions
static inline and take struct sio_register rather than sio channel
- use proper integer type (uint16_t) for getsiocsr() as siotty.c
- handle channel dependent CR2A and CR2B registers properly
- use more explicit definitions for RR_* macro used by getsiocsr()
- define and use proper RR0 (read register) values
(there is no isStatusReg(r) macro used on 4.4BSD/luna68k)

Tested on LUNA with both wscons console and serial console.

Misc cleanup of sio drivers.

- register softc of child devices as an argument of the sio interrupt
handler to avoid device_lookup_private() calls on every interrupt
- change type of sc_reg from (void *) to (struct sioreg *)
to avoid weird address offset calculations with redundant casts
- rename struct sio_softc members for consistency
- use a channel number passed via sio_attach_args in lunaws_attach()

No functional chnages. Tested on LUNA.

Use softint(9) properly to process TX/RX data between tty(4) layer.

It could cause possible locking issue to call tty(4) layer functions
from IPL_SERIAL interrupt handlers.

Changes details (mostly similar to com(4) and z8530tty(4)):
- allocate RX buffer and put data and status into it in the interrupt handler
- call t_linesw->l_rint from the software interrupt handler
- set the only first byte in siottystart() and use t_outq buffer to send
multiple TX data
- call the next t_linesw->l_start on TX complete in the software interrupt
handler

Also put more changes:
- handle cnmagic(9) properly (now entering ddb(4) by console BREAK works)
- allocate tty in the attach function as other drivers rather than first open
- use proper variable types

branches: 1.6.2; 1.6.8; 1.6.12; 1.6.16;
KNF, use uintNN_t, tab/space cosmetics etc.

- split device_t/softc and use device_t and cfdata_t etc.
- use aprint_normal(9)
- include "ioconf.h" for struct cfdriver decls
No crash on LUNA.

Remove all the __P() from sys (excluding sys/dist)
Diff checked with grep and MK1 eyeball.
i386 and amd64 GENERIC and sys still build.

branches: 1.3.8; 1.3.14;
Remove clause 3 and 4 from TNF licenses

branches: 1.2.40; 1.2.42; 1.2.44;
Kill caddr_t; there will be some MI fallout, but it will be fixed shortly.

branches: 1.1.6; 1.1.46; 1.1.84;
Introduce NetBSD/luna68k port into CVS repository.