genetlink: document parallel_ops

The kernel-doc for the parallel_ops family struct member is
missing, add it.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/genetlink.h

@@ -27,6 +27,8 @@ struct genl_info;
  * @maxattr: maximum number of attributes supported
  * @netnsok: set to true if the family can handle network
  *	namespaces and should be presented in all of them
+ * @parallel_ops: operations can be called in parallel and aren't
+ *	synchronized by the core genetlink code
  * @pre_doit: called before an operation's doit callback, it may
  *	do additional, common, filtering and return an error
  * @post_doit: called after an operation's doit callback, it may