ARM: dts: sunxi: Add de_be0 clk parent pll to simplefb node

Avoid the parent pll for the mod-clk for de_be0 getting disabled when non of
the other users are enabled (which can happens on boards when non of i2c, spi
and mmc are in use).

Note for now we point directly to the parent rather then to the de_be0 mod-clk
as that is not modelled in our devicetree yet.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>