ARM: dts: Modernize the Vexpress PL111 integration

ARM: dts: Modernize the Vexpress PL111 integration

The Versatile Express was submitted with the actual display
bridges unconnected (but defined in the device tree) and
mock "panels" encoded in the device tree node of the PL111
controller.

This doesn't even remotely describe the actual Versatile
Express hardware. Exploit the SiI9022 bridge by connecting
the PL111 pads to it, making it use EDID or fallback values
to drive the monitor.

The  also has to use the reserved memory through the
CMA pool rather than by open coding a memory region and
remapping it explicitly in the driver. To achieve this,
a reserved-memory node must exist in the root of the
device tree, so we need to pull that out of the
motherboard .dtsi include files, and push it into each
top-level device tree instead.

We do the same manouver for all the Versatile Express
boards, taking into account the different location of the
video RAM depending on which chip select is used on
each platform.

This plays nicely with the new PL111 DRM driver and
follows the standard ways of assigning bridges and
memory pools for graphics.

Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Liviu Dudau <liviu.dudau@arm.com>
Cc: Mali DP Maintainers <malidp@foss.arm.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Tested-by: Liviu Dudau <liviu.dudau@arm.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>