ARM: dts: set 'ti,set-rate-parent' for dpll4_m4 path

Set 'ti,set-rate-parent' property for clocks in the dpll4_m4 clock
path, which is used for DSS functional clock. This fixes DSS driver's
clock rate configuration, which needs the rate to be propagated properly
to the divider node (dpll4_m4_ck).

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Tested-by: Christoph Fritz <chf.fritz@googlemail.com>
Tested-by: Marek Belisko <marek@goldelico.com>
Acked-by: Tony Lindgren <tony@atomide.com>