ASoC: pcm186x: Declare PCM format with snd_pcm_format_t

The PCM format type is with __bitwise, so we should use the dedicated
snd_pcm_format_t instead of int.

This fixes the sparse warning like:
  sound/soc/codecs/pcm186x.c:268:44: warning: incorrect type in initializer (different base types)

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Mark Brown <broonie@kernel.org>