I've made some more progress in this matter. I got rid of more coreboot log errors and warning messages. I also managed to get rid off most of the warnings the linux kernel prints when it boots.
However it seems like the linux kernel can't mount the sata drives. It fails with "ata1: softreset failed (1st FIS failed)" please look at the attached logs for more info.

I find it really strange that it fails because I can use grub2 to browse the and read the sata drives without any problem.

It seems like I'm really close in getting this to work so I would be really happy if any of you guys could help me out. I don't know what I can do to fix this.

I've attached three log files coreboot_log.txt is just the coreboot log, kernel_log.txt is the what the kernel prints when it boot with my coreboot rom and kernel_vanilla.txt is with the original bios image.