sunxi: DT: A64: update device tree file for Allwinner A64 SoC

Updates the device tree file from the the Linux tree as of v4.18-rc3,
exactly Linux commit:
commit c1cff65f9b16b31e731e2e75bbe06638c86e1996
Author: Harald Geyer <harald@ccbib.org>
Date:   Thu Mar 15 16:25:08 2018 +0000

    arm64: dts: allwinner: a64: add simplefb for A64 SoC

This also pulls in the newly required include files for the clock and
reset bindings, also removes the now redundant part from our
*-u-boot.dtsi overlay file.
I kept the PWM node from U-Boot, as we recently gained this explicitly
for U-Boot's own usage and I don't want to regress here. This node is in
the queue for mainline Linux already, so the next sync will make it all
equal again.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Acked-by: Jagan Teki <jagan@amarulasolutions.com>
Tested-by: Jagan Teki <jagan@amarulasolutions.com>