pseries: Make the PAPR RTC a qdev device

At present the PAPR RTC isn't a "device" as such - it's accessed only via
firmware/hypervisor calls, and is handled in the sPAPR core code.  This
becomes inconvenient as we extend it in various ways.

This patch makes the PAPR RTC a separate device in the qemu device model.

For now, the only piece of device state - the rtc_offset - is still kept in
the global sPAPREnvironment structure.  That's clearly wrong, but leaving
it to be fixed in a following patch makes for a clearer separation between
the internal re-organization of the device, and the behavioural changes
(because the migration stream format needs to change slightly when the
offset is moved into the device's own state).

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index 0fd4912..80c6e4f 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -15,6 +15,7 @@
     QLIST_HEAD(, sPAPRPHBState) phbs;
     struct sPAPRNVRAM *nvram;
     XICSState *icp;
+    DeviceState *rtc;
 
     hwaddr ram_limit;
     void *htab;
@@ -480,7 +481,9 @@
                  uint32_t liobn, uint64_t window, uint32_t size);
 int spapr_tcet_dma_dt(void *fdt, int node_off, const char *propname,
                       sPAPRTCETable *tcet);
-void spapr_rtc_init(void);
-void spapr_rtc_read(sPAPREnvironment *spapr, struct tm *tm, uint32_t *ns);
+
+#define TYPE_SPAPR_RTC "spapr-rtc"
+
+void spapr_rtc_read(DeviceState *dev, struct tm *tm, uint32_t *ns);
 
 #endif /* !defined (__HW_SPAPR_H__) */