qmp-events: move 'MIGRATION_PASS' doc to schema

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

docs/qmp-events.txt

-                   QEMU Machine Protocol Events
-                   ============================
-
-MIGRATION_PASS
---------------
-
-Emitted from the source side of a migration at the start of each pass
-(when it syncs the dirty bitmap)
-
-Data: None.
-
-  - "pass": An incrementing count (starting at 1 on the first pass)
-
-Example:
-{"timestamp": {"seconds": 1449669631, "microseconds": 239225},
- "event": "MIGRATION_PASS", "data": {"pass": 2}}

qapi/event.json

@@ -430,6 +430,12 @@
 # @pass: An incrementing count (starting at 1 on the first pass)
 #
 # Since: 2.6
+#
+# Example:
+#
+# { "timestamp": {"seconds": 1449669631, "microseconds": 239225},
+#   "event": "MIGRATION_PASS", "data": {"pass": 2} }
+#
 ##
 { 'event': 'MIGRATION_PASS',
   'data': { 'pass': 'int' } }