add page table helpers

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
mmu v1 uses a fixes page size of 128kb

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
at this stage we do have no access to any usefull struct device

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
allocate and free page table

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
add defines for PTE bits

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>