ARM: dts: da850: add cpu node and operating points to DT

This adds a cpu node and operating points to the common da850.dtsi file.

All operating points above 300MHz are disabled by default.

Regulators need to be hooked up on a per-board basis.

Signed-off-by: David Lechner <david@lechnology.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>