ARM: dts: vf610: create generic base device trees

ARM: dts: vf610: create generic base device trees

This adds more generic base device trees for Vybrid SoCs. There
are three series of Vybrid SoC commonly available:
- VF3xx series: single core, Cortex-A5 without external memory
- VF5xx series: single core, Cortex-A5
- VF6xx series: dual core, Cortex-A5/Cortex-M4

The second digit represents the presents of a L2 cache (VFx1x).

The VF3xx series are not suitable for Linux especially since the
internal memory is quite small (1.5MiB).

The VF500 is essentially the base SoC, with only one core and
without L1 cache. The VF610 is a superset of the VF500, hence
vf500.dtsi is then included and enhanced by vf610.dtsi. There is
no board using VF510 or VF600 currently, but, if needed, they can
be added easily.

The Linux kernel can also run on the Cortex-M4 CPU of Vybrid
using !MMU support. This patchset creates a device tree structure
which allows to share peripherals nodes for a VF6xx Cortex-M4
device tree too. The two CPU types have different views of the
system: Foremost they are using different interrupt controllers,
but also the memory map is slightly different. The base device
tree vfxxx.dtsi allows to create SoC and board level device trees
supporting the Cortex-M4 while reusing the shared peripherals
nodes.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>