[SCSI] ibmmca: convert to new probing API and fix oopses

This is basically a straight conversion.  I have one of these things, so
I know it works ... my problem is that it has a wierd SCA like
connector, so I can't connect anything to it (no cables).

However, previously it panic'd in the interrupt, now it completes a bus
scan.

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>