arm64: Remove non-full-va map code

By now the code to only have a single page table level with 64k page
size and 42 bit address space is no longer used by any board in tree,
so we can safely remove it.

To clean up code, move the layerscape mmu code to the new defines,
removing redundant field definitions.

Signed-off-by: Alexander Graf <agraf@suse.de>