ALSA: AACI: use snd_pcm_lib_period_bytes()

Use the helper rather than open-coding this.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/sound/arm/aaci.c b/sound/arm/aaci.c
index 1e6d5f6..a8f9538 100644
--- a/sound/arm/aaci.c
+++ b/sound/arm/aaci.c
@@ -541,11 +541,11 @@
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct aaci_runtime *aacirun = runtime->private_data;
 
+	aacirun->period	= snd_pcm_lib_period_bytes(substream);
 	aacirun->start	= runtime->dma_area;
 	aacirun->end	= aacirun->start + snd_pcm_lib_buffer_bytes(substream);
 	aacirun->ptr	= aacirun->start;
-	aacirun->period	=
-	aacirun->bytes	= frames_to_bytes(runtime, runtime->period_size);
+	aacirun->bytes	= aacirun->period;
 
 	return 0;
 }