platform/x86: msi-laptop: Add msi_scm_model_exit() helper

The probe-error-exit and remove paths both duplicate the exact same code
to undo load_scm_model_init(). Add a helper for this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20220826111453.178962-1-hdegoede@redhat.com