mm: Show slab debug as offsets from section base not hashed pointers

Since the kernel now used hashed pointers for raw addresses, it is very
hard to guage the relative placement within a section, and since the
hash value will never match up with any contents, using it provides no
information relevant for slab debugging. Show the relative offset into
each section, so that some reference for the hexdump is provided.

References: https://gitlab.freedesktop.org/drm/intel/-/issues/8038


Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>