Convert the driver to modern style probing.  Given that there only is a
single instance for a given board that can be done using a global struct
Scsi_Host instance easily.

Also fix the removal path by passing the correct cookie to free_irq, and
enable it unconditionally.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>