[ALSA] pcm_oss - fix SNDCTL_DSP_GETOPTR not working correctly

ALSA<-OSS emulation
This patch changes snd_pcm_oss_bytes() by adding a local variable
for the frames -> bytes conversion, which means that the frame count
is no longer corrupted by this conversion.
Signed-off-by: Roger Mach <bigmach@us.ibm.com>
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>

sound/core/oss/pcm_oss.c

@@ -124,11 +124,12 @@ int snd_pcm_plugin_append(snd_pcm_plugin_t *plugin)
 
 static long snd_pcm_oss_bytes(snd_pcm_substream_t *substream, long frames)
 {
+	long bytes = 0;
 	snd_pcm_runtime_t *runtime = substream->runtime;
 	snd_pcm_uframes_t buffer_size = snd_pcm_lib_buffer_bytes(substream);
-	frames = frames_to_bytes(runtime, frames);
+	bytes = frames_to_bytes(runtime, frames);
 	if (buffer_size == runtime->oss.buffer_bytes)
-		return frames;
+		return bytes;
 	return (runtime->oss.buffer_bytes * frames) / buffer_size;
 }