trace: Add missing execution mode of guest events

Add missing execution mode documentation for the 'guest_cpu_enter' and
'guest_cpu_reset' events.

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Message-id: 147566900921.7708.656450813307396468.stgit@fimbulvetr.bsc.es
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/trace-events b/trace-events
index bd2199a..8ecded5 100644
--- a/trace-events
+++ b/trace-events
@@ -129,11 +129,13 @@
 
 # Hot-plug a new virtual (guest) CPU
 #
+# Mode: user, softmmu
 # Targets: all
 vcpu guest_cpu_enter(void)
 
 # Reset the state of a virtual (guest) CPU
 #
+# Mode: user, softmmu
 # Targets: all
 vcpu guest_cpu_reset(void)