ALSA: snd_pcm_oss_period_size: Use round{up,down}_pow_of_two()

Instead of opencoding them use the standard roundup_pow_of_two() and
rounddown_pow_of_two() helper functions. This gets rids one of the few users
of the custom ld2() function and also makes it a bit more obvious what the
code does.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/oss/pcm_oss.c

@@ -719,7 +719,7 @@ static int snd_pcm_oss_period_size(struct snd_pcm_substream *substream,
 
 	oss_buffer_size = snd_pcm_plug_client_size(substream,
 						   snd_pcm_hw_param_value_max(slave_params, SNDRV_PCM_HW_PARAM_BUFFER_SIZE, NULL)) * oss_frame_size;
-	oss_buffer_size = 1 << ld2(oss_buffer_size);
+	oss_buffer_size = rounddown_pow_of_two(oss_buffer_size);
 	if (atomic_read(&substream->mmap_count)) {
 		if (oss_buffer_size > runtime->oss.mmap_bytes)
 			oss_buffer_size = runtime->oss.mmap_bytes;
@@ -755,14 +755,14 @@ static int snd_pcm_oss_period_size(struct snd_pcm_substream *substream,
 	min_period_size = snd_pcm_plug_client_size(substream,
 						   snd_pcm_hw_param_value_min(slave_params, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, NULL));
 	min_period_size *= oss_frame_size;
-	min_period_size = 1 << (ld2(min_period_size - 1) + 1);
+	min_period_size = roundup_pow_of_two(min_period_size);
 	if (oss_period_size < min_period_size)
 		oss_period_size = min_period_size;
 
 	max_period_size = snd_pcm_plug_client_size(substream,
 						   snd_pcm_hw_param_value_max(slave_params, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, NULL));
 	max_period_size *= oss_frame_size;
-	max_period_size = 1 << ld2(max_period_size);
+	max_period_size = rounddown_pow_of_two(max_period_size);
 	if (oss_period_size > max_period_size)
 		oss_period_size = max_period_size;