Freeze compat matrix 7 for Android T

The current matrix is left in this same CL because this way, downstream
modifications to the current CL will automatically get absorbed into the
level 8 compatibility matrix. A CL on top of this will disable the 7
matrix and then get reverted in the aosp/master..goog/master merge
path.

Bug: 203103997
Test: boot, vts_treble_vintf_vendor_test
Change-Id: I5c04d26e2b4dd0aac6e7d6ce3c72496081e9539d
diff --git a/compatibility_matrices/Android.mk b/compatibility_matrices/Android.mk
index 9e715bf..d19f0da 100644
--- a/compatibility_matrices/Android.mk
+++ b/compatibility_matrices/Android.mk
@@ -102,6 +102,7 @@
     framework_compatibility_matrix.4.xml \
     framework_compatibility_matrix.5.xml \
     framework_compatibility_matrix.6.xml \
+    framework_compatibility_matrix.7.xml \
     framework_compatibility_matrix.current.xml \
     framework_compatibility_matrix.device.xml \