ARM: dts: da850: move spi0_cs3_pin pinconf node

This moves the spi0_cs3_pin pinconf node from the LEGO EV3 file to the
common DA850 include file. This node is applicable to any board, and
therefore belongs in the common file.

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