ARM: dts: use ti,fixed-factor-clock for dpll4_m5x2_mul_ck

We need to use set-rate-parent for dpll4_m5 clock path, so use the
ti,fixed-factor-clock version which supports set-rate-parent property.

The set-rate-parent flag itself is set in the following patch, this one
just changes the clock driver to ti,fixed-factor-clock without any other
changes.

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