Setup the path for v5.4 kernel

BUG=b/158772883
TEST=None
RELEASE_NOTE=None

Change-Id: I3cea01f32614251ebdae0d60efe8ea4909942981
diff --git a/external_full.xml b/external_full.xml
index c41bec4..aee3021 100644
--- a/external_full.xml
+++ b/external_full.xml
@@ -76,6 +76,9 @@
   <project path="src/third_party/kernel/v4.19"
            name="third_party/kernel"
            revision="refs/heads/cos-4.19" />
+  <project path="src/third_party/kernel/v5.4"
+           name="third_party/kernel"
+           revision="refs/heads/cos-5.4" />
 
   <repo-hooks enabled-list="pre-upload"
            in-project="mirrors/cros/chromiumos/repohooks" />