WifiDiagnostics: remove getAllRingBufferData()

This method is unused. Remove it.

BUG=27173141
TEST=wifitests/runtest.sh

Change-Id: I09a7f6f5eb9fcd60c9bd1841f7e7f2a1a2a0d5fa
diff --git a/service/java/com/android/server/wifi/WifiDiagnostics.java b/service/java/com/android/server/wifi/WifiDiagnostics.java
index f4e521f..8c0ac14 100644
--- a/service/java/com/android/server/wifi/WifiDiagnostics.java
+++ b/service/java/com/android/server/wifi/WifiDiagnostics.java
@@ -489,24 +489,6 @@
         return true;
     }
 
-    private boolean getAllRingBufferData() {
-        if (mRingBuffers == null) {
-            mLog.e("Not ring buffers available to collect data!");
-            return false;
-        }
-
-        for (WifiNative.RingBufferStatus element : mRingBuffers){
-            boolean result = mWifiNative.getRingBufferData(element.name);
-            if (!result) {
-                mLog.e("Fail to get ring buffer data of: " + element.name);
-                return false;
-            }
-        }
-
-        mLog.d("getAllRingBufferData Successfully!");
-        return true;
-    }
-
     private boolean enableVerboseLoggingForDogfood() {
         return false;
     }