* Removes default mapping of a portion of the RAM (will be done
as needed)
* Passes on the page directory area to kernel, so on early vm init
the kernel can use the area for pagetable allocation.
* Leaves it to the platform to pass in physical memory range(s). This
will ultimately come from FDT.
* Fix long standing issue with allocation of the heap, potentially
causing other part of the bootloader to overwrite the heap.
* Implements pagetable allocator in kernel for early vm mapping.
This fixes the first PANIC seen, we now just get the same one later
on when the VM is up... more to come...
