change manpage for new rfkill list behaviour
diff --git a/rfkill.8 b/rfkill.8
index 612e366..5bce9fd 100644
--- a/rfkill.8
+++ b/rfkill.8
@@ -17,8 +17,9 @@
 .B event
 Listen for rfkill events and display them on stdout.
 .TP
-.B list
-List the current state of all available rfkill-using devices.
+.B list [type]
+List the current state of all available rfkill-using devices,
+or just all of the given type.
 .TP
 .BI block " index|type"
 Disable the device corresponding to the given index.