Here are some small patches (ralative to 2.1.129) which make IDE
working on PREP Hardware especially the RiscPC (probably also needed
for MPC750).

The first problem I had was related to interrups on the RiscPC.
It always assigned IRQ13 to the IDE port. However actually the
port is connected to IRQ14. The next problem was that prep_pci.c
assigned IRQ14 to PCI. The Patch now assigns 14 to IDE and uses
9,11 and 15 for PCI. In addition to this it sets the edge/level
control according to PCI preconfiguration. In addition it adds
3 more entries to the Blackhawk table.

The second problem was that the partition table of a DOS IDE drive
was not recognized unless I specified hda=swapdata at the boot prompt.
IDE CD-Rom drives were not recognized at all. All the required coding
to operate IDE devices correctly is already there but it is not used
for PREP hardware. I changed ide.h so that PREP is handled the same
way as CHRP. This makes IDE disks and CD-roms work without the need
to specify boot options.