- seL4_UserTop is a new constant which represents the top of virtual
memory available to user level
- this commit also rationalises several constants (USER_TOP, kernelBase)
and moves them to the arch level, such that ports only need to define
seL4_UserTop.
* rename physBaseMapping to BASE_OFFSET
* because physBaseMapping was only used explicity in a few places
* move duplicated arm definions up a level
- PPTR_TOP
- PADDR_TOP
- BASE_OFFSET