cm: Update to android-7.0.0_r6

Change-Id: I72f8a577412d7aed3124648e9775305e3b68f0d2
diff --git a/default.xml b/default.xml
index 7d72a6c..237f1e8 100644
--- a/default.xml
+++ b/default.xml
@@ -11,7 +11,7 @@
   <remote  name="aosp"
            fetch="https://android.googlesource.com"
            review="android-review.googlesource.com"
-           revision="refs/tags/android-7.0.0_r1" />
+           revision="refs/tags/android-7.0.0_r6" />
 
   <default revision="refs/heads/staging/cm-14.0"
            remote="github"