Convert the WD33C93 SCSI driver core to the new irq framework (from Marc
Zyngier <mzyngier@freesurf.fr>)

This driver core is used by the following drivers:
  - M68k/PPC Amiga A3000, A2091/A590, and GVP II SCSI
  - M68k MVME147 SCSI
  - MIPS SGI IP22 (Indy, Challenge S, and Indigo 2) SCSI