Atari frame buffer device updates
  - Move static function definition before usage
  - Fix breakage caused by recent fbdev changes
  - Make some setup parameter parsing separate routines (strsep() must be able
    to modify the passed pointers)
  - On Atari the ATI Mach64 registers are memory mapped, but it's not on
    the PCI bus, so we cannot use writel() and friends.
  - Kill warnings by protecting unused data with the appropriate #ifdef
  - On Atari the ATI Mach64 registers are memory mapped, but it's not on the
    PCI bus, so we cannot use writel() and friends.
  - Fix assignment of addresses for Atari