ARM: dts: sunxi: Update simplfb nodes so that u-boot can find them

Review of the u-boot sunxi simplefb patches has led to the decision that
u-boot should not use a specific path to find the nodes as this goes contrary
to how devicetree usually works.

Instead a platform specific compatible + properties should be used for this.

The simplefb bindings have already been updated to reflect this, this patch
brings the sunxi devicetree files in line with the new binding, and the
actual u-boot implementation as it is going upstream.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v2:
-Use proper allwinner, vendor prefix instead of sunxi,
-Rename compatible to allwinner,simple-framebuffer to make clear these are
 vendor extensions to the simple-framebuffer bindings

foo
dt-bindings: simplefb: Drop the advice about using a specific path for nodes

This goes contrary to how devicetree usually works, so drop it. Instead if
the firmware needs to be able to find a specific node it should use a
platform specific compatible + properties for this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Grant Likely <grant.likely@linaro.org>
dt-bindings: simplefb-sunxi: Add sunxi simplefb extensions

If pre-filled framebuffer nodes are used, the firmware may need extra
properties to find the right node. This documents the properties to use
for this on sunxi platforms.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Grant Likely <grant.likely@linaro.org>