target/ppc: Introduce a relocation bool in ppc_radix64_handle_mmu_fault()

It will ease the introduction of new routines for partition-scoped
Radix translation.

Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20200330094946.24678-3-clg@kaod.org>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>