trivial: fix header files

Signed-off-by: Curtis Millar <curtis.millar@data61.csiro.au>

Remove references to kernelBase

kernelBase was used inconsistently between different architectures to
refer to the either of the first kernel address or the first address of
the mappings of the kernel ELF region specifically.

These have been replaced with more consistent use of constants
explicitly describing which region is being referenced.

Signed-off-by: Curtis Millar <curtis.millar@data61.csiro.au>

Consolidate kernel virtual memory regions

Each architecture now only needs to describe the bounds of the three
memory regions: the 1:1 mapped physical memory region, the kernel ELF
region (which may or may not overlap the physical memory region) and the
device / kernel page table region.

The physical base address of the 1:1 mapped physcial memory region and
the kernel ELF region must also be specified.

The top of user addressable memory (where in the same virtual address
space as the kernel) is defined by USER_TOP.

The physic memory virtual mapping is described by PPTR_BASE and
PPTR_TOP. The base physical memory address is PADDR_BASE and is the
physical address used to map PPTR_BASE.

Don't use kernelBase when referring to the base of the 1:1 mapped
physical memory window.

The kernel ELF virtual address region is described by KERNEL_ELF_BASE
and extends until the virtual address of the symbol `ki_end` which is
created by the linker. KERNEL_ELF_PADDR_BASE is the base address of
the physical memory region used to map the kernel and is the address to
which KERNEL_ELF_BASE maps.

KERNEL_ELF_BASE and KERNEL_ELF_PADDR_BASE do not need to be aligned to a
page size boundary as they are approriately truncated during boot by the
`map_kernel_window` function.

KDEV_BASE describes the base virtual address of the kernel device region
and the region is assumed to extend to the end of virtual memory.

Note: The offset between PPTR_BASE and PADDR_BASE is used to translate
the virtual address of all untyped objects to physical addresses. This
includes device untyped objects or frame objects where the virtual
address does not fall within the 1:1 mapped physical memory region.

Signed-off-by: Curtis Millar <curtis.millar@data61.csiro.au>