KVM: PPC: Book3S PR: Rework kvmppc_mmu_book3s_64_xlate()

This reworks kvmppc_mmu_book3s_64_xlate() to make it check the large
page bit in the hashed page table entries (HPTEs) it looks at, and
to simplify and streamline the code.  The checking of the first dword
of each HPTE is now done with a single mask and compare operation,
and all the code dealing with the matching HPTE, if we find one,
is consolidated in one place in the main line of the function flow.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>