[seL4] Incorrect dtb in the Microkit tutorial

Hello,

It seems that the linux.dtb file supplied with the tutorial code is not correct and does not allocate enough memory for the initrd. The symptoms this issue caused when attempting to run part4 was that the libresolv.so.2 could not be opened and the vmm panic'ed. The linux.dtb supplied in the 'solution' folder in the git repository has 'initrd-end' set to a larger value and this version does work.

Thanks,

Luke