[9fans] Soekris 5501s (was kenfs)

[geoff@plan9.bell-labs.com]

We have about a dozen Soekris 5501-70s here.  We bought the first ones
a few months ago, and have fixed or finished a few things as a result.
Some of our machines have laptop IDE disks in them and most have
compact flash cards to hold at least nvram, for booting as cpu
servers.

Sape was inspired to finish USB OHCI support, since the 5501s have no
UHCI controllers.

There's something a little odd about the serial console.  It tries to
interpret characters written to the (normally non-existent) CGA
display and emit them on the serial console.  We ended up running the
serial consoles at 9600 baud and tweaking 9load to set this speed
early on, since otherwise we lost console output for a time.

We have used at least 3 of the 4 Ethernet ports concurrently.  The
four Ethernet interfaces are 10/100Mb/s `VIA Technology VT6105M Rhine
III Management Adapters' (PCI vendor id 1106 and device id 3053).
They work fine with the current ethervt6102.c except that it doesn't
seem to initialise them perfectly correctly, and once in a while at
boot time they stop talking; power cycling the machine usually
corrects the problem.

Independently of that problem, the machines don't always come up
reliably after cycling their power.

The built-in controllers are all AMD CS5536 parts (vendor id 1022).
The IDE controller (which has a SATA connector on the motherboard) is
device id 209a, the OHCI is 2094, and the EHCI is 2095.

The optional (S)ATA disk can probably be jumpered to be either master
or slave, but the only way I know to set the compact flash card's
master/slave setting is via the BIOS (`set flash=primary' or `set
flash=secondary', as I recall).  The BIOS is not a typical PC BIOS
because there is no built-in VGA controller on the motherboard, though
there is a PCI slot into which one could insert a VGA card (we haven't
yet).  The BIOS does implement PXE booting and we use that.