fmt 0 is perfectly valid (PCM3168A_FMT_I2S). Remove the return in case
fmt == 0.

Fixes: ("ASoC: pcm3168a: Use fixup instead of constraint for channels and formats")
Reported-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20191015090037.23271-1-peter.ujfalusi@ti.comSigned-off-by: Mark Brown <broonie@kernel.org>