target/riscv: move satp_mode.{map,init} out of CPUConfig

target/riscv: move satp_mode.{map,init} out of CPUConfig

They are used to provide the nice QOM properties for svNN,
but the canonical source of the CPU configuration is now
cpu->cfg.max_satp_mode.  Store them in the ArchCPU struct.

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>