Increase the minimum alsa buffer size as we get underrun with some ap…

…ps (e.g. espeak)

sound/arm/bcm2835-pcm.c

@@ -27,7 +27,7 @@ static struct snd_pcm_hardware snd_bcm2835_playback_hw = {
 	.channels_min = 1,
 	.channels_max = 2,
 	.buffer_bytes_max = 32 * 1024,	/* Needs to be less than audioplay buffer size */
-	.period_bytes_min = 1 * 1024,
+	.period_bytes_min =  4 * 1024,
 	.period_bytes_max = 32 * 1024,
 	.periods_min = 1,
 	.periods_max = 32,