ppc: Move spapr-related prototypes from xics.h into a seperate header file

ppc: Move spapr-related prototypes from xics.h into a seperate header file

When compiling with Clang in -std=gnu99 mode, there is a warning/error:

  CC      ppc64-softmmu/hw/intc/xics_spapr.o
In file included from /home/thuth/devel/qemu/hw/intc/xics_spapr.c:34:
/home/thuth/devel/qemu/include/hw/ppc/xics.h:203:34: error: redefinition of typedef 'sPAPRMachineState' is a C11 feature
      [-Werror,-Wtypedef-redefinition]
typedef struct sPAPRMachineState sPAPRMachineState;
                                 ^
/home/thuth/devel/qemu/include/hw/ppc/spapr_irq.h:25:34: note: previous definition is here
typedef struct sPAPRMachineState sPAPRMachineState;
                                 ^

We have to remove the duplicated typedef here and include "spapr.h" instead.
But "spapr.h" should not be included for the pnv machine files. So move
the spapr-related prototypes into a new file called "xics_spapr.h" instead.

Reviewed-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>