qapi-schema: Use BlockdevSnapshot type for blockdev-snapshot-sync

We don't have to duplicate the definition any more now that we may refer
to a type instead.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMichael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: NLuiz Capitulino <lcapitulino@redhat.com>

qapi-schema.json

@@ -1709,16 +1709,7 @@
 #
 # Generates a synchronous snapshot of a block device.
 #
-# @device:  the name of the device to generate the snapshot from.
-#
-# @snapshot-file: the target of the new image. If the file exists, or if it
-#                 is a device, the snapshot will be created in the existing
-#                 file/device. If does not exist, a new file will be created.
-#
-# @format: #optional the format of the snapshot image, default is 'qcow2'.
-#
-# @mode: #optional whether and how QEMU should create a new image, default is
-#        'absolute-paths'.
+# For the arguments, see the documentation of BlockdevSnapshot.
 #
 # Returns: nothing on success
 #          If @device is not a valid block device, DeviceNotFound
@@ -1726,8 +1717,7 @@
 # Since 0.14.0
 ##
 { 'command': 'blockdev-snapshot-sync',
-  'data': { 'device': 'str', 'snapshot-file': 'str', '*format': 'str',
-            '*mode': 'NewImageMode'} }
+  'data': 'BlockdevSnapshot' }
 
 ##
 # @human-monitor-command: