I've managed to get it to boot into grub now. Seems like the problem was that I forgot to init rs780 in romstage. However now the linux kernel panics because it seems like it can find the hdds.
I also managed to solve the AGESA arrests that was happening. But it doesn't seem to have any effect on the boot process.
I've attatched the boot log. It would be really helpful if I could get some help as I have no idea why it can load grub and read the kernel image from disk but not read the disk themselfs for the linux kernel.
Note also that it doesn't matter if I boot the disks in IDE or AHCI mode. The same error happens.