mmu-hash32: Split out handling of direct store segments

mmu-hash32: Split out handling of direct store segments

At present a large chunk of ppc_hash32_translate() is taken up with an
ugly if selecting between direct store segments (hardly ever used) and
normal paged segments.  This patch clarifies the flow of code by
handling direct store segments immediately then returning, leaving the
straight line code to describe the normal MMU path.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>