Shortens the key length in HdmiControlService

The key length for SystemProperties should not be over 31

Bug: 16274152
Change-Id: I25ffaf2fc502819a7aea12372717cd00497fd3be
diff --git a/services/core/java/com/android/server/hdmi/Constants.java b/services/core/java/com/android/server/hdmi/Constants.java
index 3028100..384cd4a 100644
--- a/services/core/java/com/android/server/hdmi/Constants.java
+++ b/services/core/java/com/android/server/hdmi/Constants.java
@@ -203,8 +203,8 @@
     //       in config.xml to allow customization.
     static final int IRT_MS = 300;
 
-    static final String PROPERTY_PREFERRED_ADDRESS_PLAYBACK = "hdmi_cec.preferred_address.playback";
-    static final String PROPERTY_PREFERRED_ADDRESS_TV = "hdmi_cec.preferred_address.tv";
+    static final String PROPERTY_PREFERRED_ADDRESS_PLAYBACK = "hdmi_cec.prefaddr.playback";
+    static final String PROPERTY_PREFERRED_ADDRESS_TV = "hdmi_cec.prefaddr.tv";
 
     private Constants() { /* cannot be instantiated */ }
 }