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>