mem: Explicitly specify the endianness in the abstract memory.

mem: Explicitly specify the endianness in the abstract memory.

The accessors are used for debugging output. If we're using an ISA
where there's an endianness, we use that explicitly, falling back to a
binary dump if the size isn't supported. If not, then we just dump the
data without interpretation regardless of size.

Change-Id: Ib050c4c876ee41f17cfd14ad657150bf6ab1de39
Reviewed-on: https://gem5-review.googlesource.com/c/13464
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>