spapr: add hcalls support for the XIVE exploitation interrupt mode

spapr: add hcalls support for the XIVE exploitation interrupt mode

The different XIVE virtualization structures (sources and event queues)
are configured with a set of Hypervisor calls :

 - H_INT_GET_SOURCE_INFO

   used to obtain the address of the MMIO page of the Event State
   Buffer (ESB) entry associated with the source.

 - H_INT_SET_SOURCE_CONFIG

   assigns a source to a "target".

 - H_INT_GET_SOURCE_CONFIG

   determines which "target" and "priority" is assigned to a source

 - H_INT_GET_QUEUE_INFO

   returns the address of the notification management page associated
   with the specified "target" and "priority".

 - H_INT_SET_QUEUE_CONFIG

   sets or resets the event queue for a given "target" and "priority".
   It is also used to set the notification configuration associated
   with the queue, only unconditional notification is supported for
   the moment. Reset is performed with a queue size of 0 and queueing
   is disabled in that case.

 - H_INT_GET_QUEUE_CONFIG

   returns the queue settings for a given "target" and "priority".

 - H_INT_RESET

   resets all of the guest's internal interrupt structures to their
   initial state, losing all configuration set via the hcalls
   H_INT_SET_SOURCE_CONFIG and H_INT_SET_QUEUE_CONFIG.

 - H_INT_SYNC

   issue a synchronisation on a source to make sure all notifications
   have reached their queue.

Calls that still need to be addressed :

   H_INT_SET_OS_REPORTING_LINE
   H_INT_GET_OS_REPORTING_LINE

See the code for more documentation on each hcall.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
[dwg: Folded in fix for field accessors]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>