manifest: Add the kernel repo

BUG=b/143358600
TEST=`repo sync` checks out the kernel to the correct location.

Change-Id: I8d672e52f9a98bb11a603cba132c579b61aa9625
diff --git a/external_full.xml b/external_full.xml
index 722531f..4387582 100644
--- a/external_full.xml
+++ b/external_full.xml
@@ -70,12 +70,9 @@
   <project path="manifest" name="cos/manifest" >
       <copyfile src="LICENSE" dest="LICENSE" />
   </project>
-
-  <!--
-     -<project path="src/third_party/kernel"
-     -         name="third_party/kernel"
-     -         revision="refs/heads/lakitu-4.19" />
-     -->
+  <project path="src/third_party/kernel/v4.19"
+           name="third_party/kernel"
+           revision="refs/heads/cos-4.19" />
 
   <repo-hooks enabled-list="pre-upload"
            in-project="mirrors/cros/chromiumos/repohooks" />