kernel: Add cos_patch_trailer_check repohook check.

BUG=b/179054156
TEST=local testing
RELEASE_NOTE=None

Change-Id: I73dce2ecb790fb947d420f85e41b9c8bdc0d2007
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/11877
Reviewed-by: Dexter Rivera <riverade@google.com>
Tested-by: Vaibhav Rustagi <vaibhavrustagi@google.com>
diff --git a/PRESUBMIT.cfg b/PRESUBMIT.cfg
index 0d7269b..fe19a16 100644
--- a/PRESUBMIT.cfg
+++ b/PRESUBMIT.cfg
@@ -7,5 +7,8 @@
 tabbed_indent_required_check: false
 signoff_check: true
 
+# Make sure cos_patch trailer is present.
+cos_patch_trailer_check: true
+
 # Make sure RELEASE_NOTE field is present.
 release_note_field_check: true