reduce safe headphone volume index...

EQ preset with max gains was still above the 27mV limit.

Bug 7064975.

Change-Id: If85f082bab89c9d74ba0b7f5979c891180469ce4
diff --git a/overlay/frameworks/base/core/res/res/values/config.xml b/overlay/frameworks/base/core/res/res/values/config.xml
index 88f593b..f7b8c3b 100644
--- a/overlay/frameworks/base/core/res/res/values/config.xml
+++ b/overlay/frameworks/base/core/res/res/values/config.xml
@@ -228,7 +228,7 @@
     </string-array>
 
     <!-- reference volume index for music stream to limit headphone volume and display warning -->
-    <integer name="config_safe_media_volume_index">8</integer>
+    <integer name="config_safe_media_volume_index">7</integer>
 
     <bool name="config_enableWifiDisplay">true</bool>