target-ppc: Move cpu_exec_init() call to realize function

target-ppc: Move cpu_exec_init() call to realize function

Move cpu_exec_init() call from instance_init to realize. This allows
any failures from cpu_exec_init() to be handled appropriately.
Also add corresponding cpu_exec_exit() call from unrealize.

cpu_dt_id assignment from instance_init is no longer needed since
correct assignment for cpu_dt_id is already present in realizefn.

Signed-off-by: Bharata B Rao <[email protected]>
Reviewed-by: David Gibson <[email protected]>
Reviewed-by: Peter Crosthwaite <[email protected]>
Acked-by: Paolo Bonzini <[email protected]>
Signed-off-by: Peter Crosthwaite <[email protected]>
[AF: Keep calling cpu_exec_init() for CONFIG_USER_ONLY]
Signed-off-by: Andreas Färber <[email protected]>