linux-phytec-fsl

xtensa: move kernel mapping addresses into kmem_layout.h

Create a header dedicated to memory layout definitions. Include it from
places where these definitions are needed.
Express vmalloc area address, VIRTUAL_MEMORY_ADDRESS and KERNELOFFSET
through KSEG address.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>