So I thought maybe the iMac has a bluetooth controller which has been installed into the OS but the white macbook don't so I deleted the kext file but still not booting with the following error message appeared:
So I thought maybe the kernel extensions are not compatible or the kernel is different... Messing around with mach_kernels and /System/Library/Extension folder It got me nowhere and I lost a whole business day with no results. So I tried different things but in the end I found the following solution: The iMac Lion installation was a very early one 10.7.1 and was never really updated. Also I taught that maybe I have to clean up all the systems caches because the hardware seems to be really different. So first thing I updated the iMac Lion installation to the latest Mac Os X 10.7.5 and updated all software trough the "Software Updates" program. Then I installed CCleaner and deleted all unnecessary files, languages and repaired the permissions. Then I zeroed out the free space in order to get a smaller dmg. After that I installed Onyx and cleaned out all the system caches (Kernel, Boot, etc). I repaired the permissions with this program once again. After that I created the dmg dump using Disk Utility again and installed it on the white macbook. And it worked! Now it booted up nicely and works 100%. So in the end I think it was due to some cache files which were still there from the iMac or maybe just the old operating system number. So what I have learned is if you want to transfer/migrate an existing OS X installation from one mac to another tidy up the system first!!!
'could not find driver for platform AHCI'.