Update PRESUBMIT.cfg to include checks for release_notes.

Also, remove checkpatch and signed-off as they always
complain about 'Signed-off' tag which is not necessary
to be present everytime.

BUG=b/173034990
TEST=manually checking on some changelists.
RELEASE_NOTE=None

Change-Id: I04e0e284847adb8476edea36449ba835ae6d1010
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/8662
Reviewed-by: Dexter Rivera <riverade@google.com>
Tested-by: Vaibhav Rustagi <vaibhavrustagi@google.com>
diff --git a/PRESUBMIT.cfg b/PRESUBMIT.cfg
index c683529..4b553ba 100644
--- a/PRESUBMIT.cfg
+++ b/PRESUBMIT.cfg
@@ -1,8 +1,10 @@
 [Hook Overrides]
-checkpatch_check: true
 aosp_license_check: false
 cros_license_check: false
 long_line_check: false
 stray_whitespace_check: false
 tab_check: false
 tabbed_indent_required_check: false
+
+# Make sure RELEASE_NOTE field is present.
+release_note_field_check: true
\ No newline at end of file