Reorgenize boot device configuration.  The idea is taken from OpenBSD/luna88k.

- remove kernel-like autoconfiguration to probe bootable devices
- initialize SCSI and Ethernet controllers statically instead
- probe and print all SCSI disks (but don't assign unit numbers)
- make sdopen() to recheck the device and allocate softc dynamically
- use controller number and SCSI target ID (ctlr * 10 + id) to specify
  the boot disk on the "boot" command arg
- bump version to denote changes

Now bootloader works as the following:
---
>> NetBSD/luna68k boot, Revision 1.8 (Wed Jan  8 23:16:21 JST 2014)
>> (based on Stinger ver 0.0 [Phase-31])

Machine model   = LUNA-II
Physical Memory = 0x4000000  (64 MB)

sc0 at 0xe1000000: async, parity, ID 7
 ID 3: TEAC FC-1     HGF  10 rev , 512 bytes/sect x 2879 sectors
 ID 6: IBM DPES-31080 rev S31Q, 512 bytes/sect x 2118143 sectors
sc1 at 0xe1000040: async, parity, ID 7
 ID 6: MELCO DSC-G rev 1.00, 512 bytes/sect x 62533295 sectors
le0: Am7990 LANCE Ethernet, mem at 0x71010000
le0: Ethernet address = 00:00:0a:03:42:77

Press return to boot now, any other key for boot menu
booting sd(16,0)netbsd - starting in 0 seconds.
auto-boot sd(16,0)netbsd
1911696+96040 [280480+159179]=0x255a30
 :