trace: [ust] fix generation of 'trace.c' on events without args

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

scripts/tracetool

@@ -338,14 +338,15 @@ linetoc_ust()
     name=$(get_name "$1")
     args=$(get_args "$1")
     argnames=$(get_argnames "$1", ",")
+    [ -z "$argnames" ] || argnames=", $argnames"
     fmt=$(get_fmt "$1")
 
     cat <<EOF
 DEFINE_TRACE(ust_$name);
 
 static void ust_${name}_probe($args)
 {
-    trace_mark(ust, $name, "$fmt", $argnames);
+    trace_mark(ust, $name, "$fmt"$argnames);
 }
 EOF
 
@@ -488,7 +489,7 @@ EOF
         cat <<EOF
   $arg = \$arg$i;
 EOF
-	i="$((i+1))"
+        i="$((i+1))"
     done
 
     cat <<EOF
@@ -585,7 +586,7 @@ tracetostap()
        exit 1
     fi
     if [ -z "$probeprefix" ]; then
-	probeprefix="qemu.$targettype.$targetarch";
+        probeprefix="qemu.$targettype.$targetarch";
     fi
     echo "/* This file is autogenerated by tracetool, do not edit. */"
     convert stap