hw/rtc/mc146818rtc: Drop pre-v3 migration stream support

mc146818rtc's migration stream is at version 3 since commit
56038ef623 ("RTC: Update the RTC clock only when reading it")
from 12 years ago, released in QEMU v1.3.0!
No versioned machines are that old, we can safely remove
support for older streams and the qdev_set_legacy_instance_id()
call.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Message-ID: <20250115210048.25396-1-philmd@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>

hw/rtc/mc146818rtc.c

@@ -819,7 +819,7 @@ static const VMStateDescription vmstate_rtc_irq_reinject_on_ack_count = {
 static const VMStateDescription vmstate_rtc = {
     .name = "mc146818rtc",
     .version_id = 3,
-    .minimum_version_id = 1,
+    .minimum_version_id = 3,
     .pre_save = rtc_pre_save,
     .post_load = rtc_post_load,
     .fields = (const VMStateField[]) {
@@ -829,13 +829,13 @@ static const VMStateDescription vmstate_rtc = {
         VMSTATE_TIMER_PTR(periodic_timer, MC146818RtcState),
         VMSTATE_INT64(next_periodic_time, MC146818RtcState),
         VMSTATE_UNUSED(3*8),
-        VMSTATE_UINT32_V(irq_coalesced, MC146818RtcState, 2),
-        VMSTATE_UINT32_V(period, MC146818RtcState, 2),
-        VMSTATE_UINT64_V(base_rtc, MC146818RtcState, 3),
-        VMSTATE_UINT64_V(last_update, MC146818RtcState, 3),
-        VMSTATE_INT64_V(offset, MC146818RtcState, 3),
-        VMSTATE_TIMER_PTR_V(update_timer, MC146818RtcState, 3),
-        VMSTATE_UINT64_V(next_alarm_time, MC146818RtcState, 3),
+        VMSTATE_UINT32(irq_coalesced, MC146818RtcState),
+        VMSTATE_UINT32(period, MC146818RtcState),
+        VMSTATE_UINT64(base_rtc, MC146818RtcState),
+        VMSTATE_UINT64(last_update, MC146818RtcState),
+        VMSTATE_INT64(offset, MC146818RtcState),
+        VMSTATE_TIMER_PTR(update_timer, MC146818RtcState),
+        VMSTATE_UINT64(next_alarm_time, MC146818RtcState),
         VMSTATE_END_OF_LIST()
     },
     .subsections = (const VMStateDescription * const []) {
@@ -929,8 +929,6 @@ static void rtc_realizefn(DeviceState *dev, Error **errp)
     memory_region_add_subregion(&s->io, 0, &s->coalesced_io);
     memory_region_add_coalescing(&s->coalesced_io, 0, 1);
 
-    qdev_set_legacy_instance_id(dev, s->io_base, 3);
-
     object_property_add_tm(OBJECT(s), "date", rtc_get_date);
 
     qdev_init_gpio_out(dev, &s->irq, 1);