ASoC: soc-generic-dmaengine-pcm: Fix sparse warnings

Currently the following sparse warnings are observed:

sound/soc/soc-generic-dmaengine-pcm.c:185:34: warning: restricted snd_pcm_format_t degrades to integer
sound/soc/soc-generic-dmaengine-pcm.c:186:66: warning: incorrect type in argument 1 (different base types)
sound/soc/soc-generic-dmaengine-pcm.c:186:66:    expected restricted snd_pcm_format_t [usertype] format
sound/soc/soc-generic-dmaengine-pcm.c:186:66:    got int [signed] [assigned] i

Fix it by changing the loop variable to be of 'snd_pcm_format_t'.

Also introduce a SNDRV_PCM_FORMAT_FIRST label, which corresponds to the
first member (index 0) of the snd_pcm_format_t formats.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h
index 07d6158..ed0a120 100644
--- a/include/uapi/sound/asound.h
+++ b/include/uapi/sound/asound.h
@@ -242,6 +242,7 @@ typedef int __bitwise snd_pcm_format_t;
 #define	SNDRV_PCM_FORMAT_DSD_U16_BE	((__force snd_pcm_format_t) 51) /* DSD, 2-byte samples DSD (x16), big endian */
 #define	SNDRV_PCM_FORMAT_DSD_U32_BE	((__force snd_pcm_format_t) 52) /* DSD, 4-byte samples DSD (x32), big endian */
 #define	SNDRV_PCM_FORMAT_LAST		SNDRV_PCM_FORMAT_DSD_U32_BE
+#define	SNDRV_PCM_FORMAT_FIRST		SNDRV_PCM_FORMAT_S8
 
 #ifdef SNDRV_LITTLE_ENDIAN
 #define	SNDRV_PCM_FORMAT_S16		SNDRV_PCM_FORMAT_S16_LE