target/ppc: Extend ppc_radix64_check_prot() with a 'partition_scoped' bool

This prepares ground for partition-scoped Radix translation.

Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Greg Kurz <groug@kaod.org>
Message-Id: <20200403140056.59465-3-clg@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>