sound: dmasound_atari: Mark expected switch fall-through

Mark switch cases where we are expecting to fall through.

This patch fixes the following warning (Building: m68k):

sound/oss/dmasound/dmasound_atari.c: warning: this statement may fall
through [-Wimplicit-fallthrough=]:  => 1449:24

Notice that, in this particular case, the code comment is
modified in accordance with what GCC is expecting to find.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/oss/dmasound/dmasound_atari.c

@@ -1432,25 +1432,25 @@ static int FalconMixerIoctl(u_int cmd, u_long arg)
 {
 	int data;
 	switch (cmd) {
-	    case SOUND_MIXER_READ_RECMASK:
+	case SOUND_MIXER_READ_RECMASK:
 		return IOCTL_OUT(arg, SOUND_MASK_MIC);
-	    case SOUND_MIXER_READ_DEVMASK:
+	case SOUND_MIXER_READ_DEVMASK:
 		return IOCTL_OUT(arg, SOUND_MASK_VOLUME | SOUND_MASK_MIC | SOUND_MASK_SPEAKER);
-	    case SOUND_MIXER_READ_STEREODEVS:
+	case SOUND_MIXER_READ_STEREODEVS:
 		return IOCTL_OUT(arg, SOUND_MASK_VOLUME | SOUND_MASK_MIC);
-	    case SOUND_MIXER_READ_VOLUME:
+	case SOUND_MIXER_READ_VOLUME:
 		return IOCTL_OUT(arg,
 			VOLUME_ATT_TO_VOXWARE(dmasound.volume_left) |
 			VOLUME_ATT_TO_VOXWARE(dmasound.volume_right) << 8);
-	    case SOUND_MIXER_READ_CAPS:
+	case SOUND_MIXER_READ_CAPS:
 		return IOCTL_OUT(arg, SOUND_CAP_EXCL_INPUT);
-	    case SOUND_MIXER_WRITE_MIC:
+	case SOUND_MIXER_WRITE_MIC:
 		IOCTL_IN(arg, data);
 		tt_dmasnd.input_gain =
 			RECLEVEL_VOXWARE_TO_GAIN(data & 0xff) << 4 |
 			RECLEVEL_VOXWARE_TO_GAIN(data >> 8 & 0xff);
-		/* fall thru, return set value */
-	    case SOUND_MIXER_READ_MIC:
+		/* fall through - return set value */
+	case SOUND_MIXER_READ_MIC:
 		return IOCTL_OUT(arg,
 			RECLEVEL_GAIN_TO_VOXWARE(tt_dmasnd.input_gain >> 4 & 0xf) |
 			RECLEVEL_GAIN_TO_VOXWARE(tt_dmasnd.input_gain & 0xf) << 8);