ARM: dts: da850: add a node for the LCD controller

Add pins used by the LCD controller and a disabled LCDC node to be
reused in device trees including da850.dtsi.

Signed-off-by: Karl Beldan <kbeldan@baylibre.com>
[Bartosz:
  - added the commit description
  - changed the dt node name to a generic one
  - added a da850-specific compatible string
  - removed the tilcdc,panel node
  - moved the pins definitions to da850.dtsi as suggested by
    Sekhar Nori (was in: da850-lcdk.dts)]
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
[nsekhar@ti.com: fix compatible property and remove interrupt-parent]
Signed-off-by: Sekhar Nori <nsekhar@ti.com>