ARM: dts: vf6xx: Cosmic+: M4(nommu) initial support

Minimal Cortex-M4 device tree to boot Linux to shell. M4 is booted via
Cortex-A5 running Linux using Stefan Agner's <stefan@agner.ch> "m4boot"
utility.

Signed-off-by: Afzal Mohammed <afzal.mohd.ma@gmail.com>
Acked-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>