ASoC: Intel: do cast earlier in sst_cdev_tstamp()

My static checker complains about these because it looks like the
multiply can overflow and then we cast to a larger data type.  I don't
think this is a problem, but it's also harmless to do the cast earlier
so let's silence the static checker warning.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/intel/atom/sst/sst_drv_interface.c

@@ -381,7 +381,7 @@ static int sst_cdev_tstamp(struct device *dev, unsigned int str_id,
 	tstamp->copied_total = fw_tstamp.ring_buffer_counter;
 	tstamp->pcm_frames = fw_tstamp.frames_decoded;
 	tstamp->pcm_io_frames = div_u64(fw_tstamp.hardware_counter,
-			(u64)((stream->num_ch) * SST_GET_BYTES_PER_SAMPLE(24)));
+			(u64)stream->num_ch * SST_GET_BYTES_PER_SAMPLE(24));
 	tstamp->sampling_rate = fw_tstamp.sampling_frequency;
 
 	dev_dbg(dev, "PCM  = %u\n", tstamp->pcm_io_frames);