ARM: dts: set 'ti,set-rate-parent' for dpll4_m5 path

Set 'ti,set-rate-parent' property for the dpll4_m5x2_mul_ck clock, which
is used for the ISP functional clock. This fixes the OMAP3 ISP driver's
clock rate configuration, which needs the rate to be propagated properly
to the divider node (dpll4_m5_ck).

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>