ARM: dts: da850-lego-ev3: remove unnecessary gpio-keys properties

This removes the #address-cells and #size-cells properties from the
gpio-keys node in the da850-lego-ev3 device tree. These properties are
not needed since the child nodes don't have a reg property.

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