mmu-hash*: Make find_pte{32, 64} do more of the job of finding ptes

find_pte{32,64}() are not particularly well named.  They only "find" a PTE
within a given PTE group, and they also do permissions checking and other
things.

This patch makes it somewhat close to matching the name, by folding the
search of both primary and secondary hash bucket into it, along with the
various address bit shuffling to determine the right hash buckets.

In the 32-bit case we also remove the code for splitting large pages into
4k pieces for the qemu tlb, since no 32-bit hash MMUs support multiple page
sizes.

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