ASoC: Tegra: sparse cleanup

Fixes the following sparse warnings:

sound/soc/tegra/tegra_das.c:215:8: warning: Using plain integer as NULL pointer
sound/soc/tegra/tegra_das.c:237:8: warning: Using plain integer as NULL pointer
sound/soc/tegra/tegra_pcm.c:370:32: warning: symbol 'tegra_pcm_platform' was not declared. Should it be static?

Signed-off-by: Olof Johansson <olof@lixom.net>
Acked-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/tegra/tegra_das.c

@@ -212,7 +212,7 @@ err_release:
 	release_mem_region(res->start, resource_size(res));
 err_free:
 	kfree(das);
-	das = 0;
+	das = NULL;
 exit:
 	return ret;
 }
@@ -234,7 +234,7 @@ static int __devexit tegra_das_remove(struct platform_device *pdev)
 	release_mem_region(res->start, resource_size(res));
 
 	kfree(das);
-	das = 0;
+	das = NULL;
 
 	return 0;
 }

sound/soc/tegra/tegra_pcm.c

@@ -367,7 +367,7 @@ static void tegra_pcm_free(struct snd_pcm *pcm)
 	tegra_pcm_deallocate_dma_buffer(pcm, SNDRV_PCM_STREAM_PLAYBACK);
 }
 
-struct snd_soc_platform_driver tegra_pcm_platform = {
+static struct snd_soc_platform_driver tegra_pcm_platform = {
 	.ops		= &tegra_pcm_ops,
 	.pcm_new	= tegra_pcm_new,
 	.pcm_free	= tegra_pcm_free,