KVM: PPC: Make iommu_table::it_userspace big endian

We are going to reuse multilevel TCE code for the userspace copy of
the TCE table and since it is big endian, let's make the copy big endian
too.

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Acked-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>