mfd: ucb1400 sound driver uses/depends on AC97_BUS:

ERROR: "ac97_bus_type" [drivers/mfd/ucb1400_core.ko] undefined!

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Samuel Ortiz <sameo@openedhand.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>