ARM: dts: cygnus: enable iproc-hwrng

Enable the HW rng driver "iproc-rng200" for all cygnus platforms.

Signed-off-by: Mohamed Ismail Abdul Packir Mohamed <mohamed-ismail.abdul@broadcom.com>
Reviewed-by: Ray Jui <ray.jui@broadcom.com>
Signed-off-by: Scott Branden <scott.branden@broadcom.com>
Tested-by: Clément Péron <peron.clem@gmail.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>