RouterBoard 133 support

Hi Folks,

I've been hacking the last two days my RouterBoard 133. I've made a 
couple of fixes on a private tree to adapt RB153 config. Code is 
available there:

http://github.com/lacombar/netbsd-alc/commits/rb133-fix

The biggest problem I encountered is the network. More precisely, the 
kernel does not map the external ports the same way the bootloader does. 
It resulting in a need to move the ethernet plug during boot. The code 
is also missing the bits to detect notification from hardware (in 
particular handling of the PSC interrupt). I'll try to have a better 
look at this in the coming days.

I didn't try yet any PCI devices on the board.

  - Arnaud

ps: is there a way to enforce arch endianness and fails if a wrong one 
is used? evbmips has no default MACHINE_ARCH, but the bootloader will 
fails with big endian kernel (the SoC endiannes is wired in hardware 
anyway).

ps2: David, what happen to `sys/arch/mips/adm5120/dev/admflash.c' ? 
There is commented reference to it in `files.adm5120' but nothing seems 
to ever have reached the CVS.