softmmu: Add missing trace-events file

Commit c7f419f584 moved softmmu-only files out of the root
directory, but forgot to move the trace events, which should
no longer be generated to "trace-root.h". Fix that by adding
softmmu/trace-events.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Claudio Fontana <cfontana@suse.de>
Reviewed-by: Claudio Fontana <cfontana@suse.de>
Message-id: 20200805130221.24487-1-philmd@redhat.com

[Rebased onto meson.
--Stefan]

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/softmmu/balloon.c b/softmmu/balloon.c
index b89646f..2345229 100644
--- a/softmmu/balloon.c
+++ b/softmmu/balloon.c
@@ -28,10 +28,10 @@
 #include "qemu/atomic.h"
 #include "sysemu/kvm.h"
 #include "sysemu/balloon.h"
-#include "trace/trace-root.h"
 #include "qapi/error.h"
 #include "qapi/qapi-commands-misc.h"
 #include "qapi/qmp/qerror.h"
+#include "trace.h"
 
 static QEMUBalloonEvent *balloon_event_fn;
 static QEMUBalloonStatus *balloon_stat_fn;