spapr: nested: Introduce H_GUEST_[GET|SET]_CAPABILITIES hcalls.

Introduce the nested PAPR hcalls:
 - H_GUEST_GET_CAPABILITIES which is used to query the capabilities
   of the API and the L2 guests it provides.
 - H_GUEST_SET_CAPABILITIES which is used to set the Guest API
   capabilities that the Host Partition supports and may use.

[amachhiw: support for p9 compat mode and return register bug fixes]

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Amit Machhiwal <amachhiw@linux.vnet.ibm.com>
Signed-off-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
3 files changed