Update NEWS file about cpuid and soundhw

Add entry to the news file, per request.
Signed-off-by: Santi Raffa <rsanti@google.com>
Reviewed-by: Helga Velroyen <helgav@google.com>

NEWS

@@ -32,6 +32,7 @@ New features
 - The move-instance command can now change disk templates when moving
   instances, and does not require any node placement options to be
   specified if the destination cluster has a default iallocator.
+- Users can now change the soundhw and cpuid settings for XEN hypervisors.
 
 Misc changes
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