[9fans] amd sb690 ahci bug with atapi

[9fans] amd sb690 ahci bug with atapi

[erik quanstrom]

there is a hardware errata with the amd 690 southbridge
that has been causing some funny results on my terminal's
dvd drive for some time now.  i finally hunted it down last night.
my contrib sd package has the fix.

unfortunately, i also happen to own a dvd drive that loves to
set check condition: no media present sense codes in response
to "test unit ready" and other commands most dvd drives just
are happy to let pass.  i believe this is the same problem that
led to this comment in sdata.c
	/* used to test as&Chk as failure too, but some CD readers use that for media change */
unfortunately, i found that it was pretty hard to just ignore
the sense code with scuzz, so i submitted a scuzz patch that ignores
no media errors, too.  (cdfs is impervious to these errors.)

- erik