KVM: PPC: Book3S HV: Make HTAB code LE host aware

When running on an LE host all data structures are kept in little endian
byte order. However, the HTAB still needs to be maintained in big endian.

So every time we access any HTAB we need to make sure we do so in the right
byte order. Fix up all accesses to manually byte swap.

Signed-off-by: Alexander Graf <agraf@suse.de>