Add <kernel> entry to framework compat mat

3.18, 4.4 and 4.9 are the supported kernels in O.

Test: builds
Test: adb shell vintf (RuntimeInfo is compatible with
 framework compat mat)

Bug: 38324908
Change-Id: I8b2c98e8168af651215a309c8b0b93d3c342f97d
diff --git a/compatibility_matrix.xml b/compatibility_matrix.xml
index ba6b659..9aa5418 100644
--- a/compatibility_matrix.xml
+++ b/compatibility_matrix.xml
@@ -319,4 +319,7 @@
             <instance>default</instance>
         </interface>
     </hal>
+    <kernel version="4.9.0" />
+    <kernel version="4.4.0" />
+    <kernel version="3.18.0" />
 </compatibility-matrix>