misc: Make decode_packet_trace.py print the new master ID fields.

Those fields are "repeated" which means they can appear zero times, which
they will in older style traces.

Change-Id: Ib6ff4aab521332cf1405549d0d6e922c51c12f32
Reviewed-on: https://gem5-review.googlesource.com/5003
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

util/decode_packet_trace.py

@@ -105,6 +105,9 @@ def main():
     print "Object id:", header.obj_id
     print "Tick frequency:", header.tick_freq
 
+    for id_string in header.id_strings:
+        print 'Master id %d: %s' % (id_string.key, id_string.value)
+
     print "Parsing packets"
 
     num_packets = 0