migration-guide: add release notes for 4.0.22

(From yocto-docs rev: f490f72b7356ae2564ca6b3f7e4f1ee515f12608)

Signed-off-by: Lee Chee Yang <chee.yang.lee@intel.com>
Reviewed-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
(cherry picked from commit 9563855ccd92e21fb6f8320c96a3a83e115c947e)
Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>

documentation/migration-guides/release-4.0.rst

@@ -28,4 +28,5 @@ Release 4.0 (kirkstone)
    release-notes-4.0.19
    release-notes-4.0.20
    release-notes-4.0.21
+   release-notes-4.0.22