[9fans] arm ports update

[geoff@plan9.bell-labs.com]

The kw port now supports the Guruplug Server Plus, including both
Ethernet interfaces, and probably the other Guruplugs.  booting(8) now
has the necessary instructions to get started.  They are more diverse
than one might like because every version of u-boot we get for a new
board seems to have had the dhcp, bootp and tftp commands tinkered
with to behave slightly differently.  We have two Guruplugs and one
has been stable but the other is prone to random resets (and runs much
warmer than the Sheevaplugs).  I'd be interested in hearing from
anyone else who sees random resets.

I've imported the flash memory support from native Inferno, other than
the flash translation layer, which was developed for nor flash and is
suspect with nand flash.  flash(3) describes the interface.  It seems
to work on the Kirkwood boards, but I haven't exercised it
extensively.  It does implement software ECC.  /dev/flash looks like
it always returns zero bytes on the igepv2 board, but lack of
documentation makes it a little hard to tell what to expect.