devicetree: bindings: add bindings for ahci-da850

Add DT bindings for the TI DA850 AHCI SATA controller.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>