spapr: nested: Extend nested_ppc_state for nested PAPR API
Currently, nested_ppc_state stores a certain set of registers and works
with nested_[load|save]_state() for state transfer as reqd for nested-hv API.
Extending these with additional registers state as reqd for nested PAPR API.
Acked-by: Nicholas Piggin <npiggin@gmail.com> Suggested-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Harsh Prateek Bora <harshpb@linux.ibm.com> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>