ASoC: pcm3168a: add HW constraint for non RIGHT_J

RIGHT_J only can handle 16bit data bits.
Current driver just errored if user requests non RIGHT_J
+ 16bit combination. But it is not useful for user.
This patch adds HW constraint for it, and avoid
error on such situation.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>