ASoC: samsung: add missing "fallthrough;"

With gcc, we get a warning in this file:

In file included from include/linux/io.h:13,
                 from sound/soc/samsung/s3c-i2s-v2.c:16:
sound/soc/samsung/s3c-i2s-v2.c: In function 's3c2412_i2s_trigger':
arch/arm/include/asm/io.h:92:22: error: this statement may fall through [-Werror=implicit-fallthrough=]
 #define __raw_writel __raw_writel
                      ^
arch/arm/include/asm/io.h:299:29: note: in expansion of macro '__raw_writel'
 #define writel_relaxed(v,c) __raw_writel((__force u32) cpu_to_le32(v),c)
                             ^~~~~~~~~~~~
arch/arm/include/asm/io.h:307:36: note: in expansion of macro 'writel_relaxed'
 #define writel(v,c)  ({ __iowmb(); writel_relaxed(v,c); })
                                    ^~~~~~~~~~~~~~
sound/soc/samsung/s3c-i2s-v2.c:398:3: note: in expansion of macro 'writel'
   writel(0x0, i2s->regs + S3C2412_IISFIC);
   ^~~~~~
sound/soc/samsung/s3c-i2s-v2.c:400:2: note: here
  case SNDRV_PCM_TRIGGER_RESUME:
  ^~~~

From all I can tell, this was indeed meant to fall through, so
add "fallthrough;" statement to avoid the warning.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210927095449.1070639-1-arnd@kernel.orgSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/samsung/s3c-i2s-v2.c

@@ -397,6 +397,8 @@ static int s3c2412_i2s_trigger(struct snd_pcm_substream *substream, int cmd,
 		/* clear again, just in case */
 		writel(0x0, i2s->regs + S3C2412_IISFIC);
 
+		fallthrough;
+
 	case SNDRV_PCM_TRIGGER_RESUME:
 	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
 		if (!i2s->master) {