hw/qdev-clock: Avoid calling qdev_connect_clock_in after DeviceRealize

Clock canonical name is set in device_set_realized (see the block
added to hw/core/qdev.c in commit 0e6934f264).
If we connect a clock after the device is realized, this code is
not executed. This is currently not a problem as this name is only
used for trace events, however this disrupt tracing.

Add a comment to document qdev_connect_clock_in() must be called
before the device is realized, and assert this condition.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20200803105647.22223-5-f4bug@amsat.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/hw/core/qdev-clock.c b/hw/core/qdev-clock.c
index f139b68..47ecb5b 100644
--- a/hw/core/qdev-clock.c
+++ b/hw/core/qdev-clock.c
@@ -186,5 +186,6 @@
 
 void qdev_connect_clock_in(DeviceState *dev, const char *name, Clock *source)
 {
+    assert(!dev->realized);
     clock_set_source(qdev_get_clock_in(dev, name), source);
 }