target/ppc: Split page size information into a separate allocation

target/ppc: Split page size information into a separate allocation

env->sps contains page size encoding information as an embedded structure.
Since this information is specific to 64-bit hash MMUs, split it out into
a separately allocated structure, to reduce the basic env size for other
cpus.  Along the way we make a few other cleanups:

    * Rename to PPCHash64Options which is more in line with qemu name
      conventions, and reflects that we're going to merge some more hash64
      mmu specific details in there in future.  Also rename its
      substructures to match qemu conventions.

    * Move structure definitions to the mmu-hash64.[ch] files.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Cédric Le Goater <clg@kaod.org>