ALSA: pcm: Simplify params_period_bytes()

The hw_params struct has a parameter that contains the period size in bytes.
This can be used instead of deriving the value from other parameters. This
is similar to e.g. params_buffer_bytes()
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

include/sound/pcm_params.h

@@ -363,9 +363,7 @@ params_subformat(const struct snd_pcm_hw_params *p)
 static inline unsigned int
 params_period_bytes(const struct snd_pcm_hw_params *p)
 {
-	return (params_period_size(p) *
-		snd_pcm_format_physical_width(params_format(p)) *
-		params_channels(p)) / 8;
+	return hw_param_interval_c(p, SNDRV_PCM_HW_PARAM_PERIOD_BYTES)->min;
 }
 
 /**