ARM: Kirkwood: Add basic device tree support for QNAP TS219.

The two different variants of QNAP TS devices, varying by SoC, put the
GPIO keys on different GPIO lines. Hence we need two different DT
board descriptions, which share the same board-ts219.c file.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Jason Cooper <jason@lakedaemon.net>