[PATCH] SGI IOC4: Detect IO card variant

There are three different IO cards which an SGI IOC4 controller may find
itself on.  One of these variants does not bring out the IDE and serial
signals, so we need to disable attaching the corresponding IOC4 subdrivers
to such cards.

Cleans up message clutter emitted during device probing.

Signed-off-by: Brent Casavant <bcasavan@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>