ARM: dts: sunxi: Add pll3 to simplefb nodes clocks lists

Now that we've a clock node describing pll3 we must add it to the
simplefb nodes clocks lists to avoid it getting turned off when
simplefb is used.

This fixes the screen going black when using simplefb.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>