ASoC: kirkwood: Remove unused drivers

Both kirkwood-openrd and kirkwood-t5325 drivers have been replaced
with DT based simple-card equivelents. So remove these drivers.

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