[PATCH] drm: sti: Mark expected switch fall-throughs

["Gustavo A. R. Silva" <gustavo@embeddedor.com>]

Mark switch cases where we are expecting to fall through.

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

drivers/gpu/drm/sti/sti_hdmi.c: In function ‘hdmi_audio_configure’:
drivers/gpu/drm/sti/sti_hdmi.c:851:13: warning: this statement may fall through [-Wimplicit-fallthrough=]
   audio_cfg |= HDMI_AUD_CFG_CH78_VALID;
drivers/gpu/drm/sti/sti_hdmi.c:852:2: note: here
  case 6:
  ^~~~
drivers/gpu/drm/sti/sti_hdmi.c:853:13: warning: this statement may fall through [-Wimplicit-fallthrough=]
   audio_cfg |= HDMI_AUD_CFG_CH56_VALID;
drivers/gpu/drm/sti/sti_hdmi.c:854:2: note: here
  case 4:
  ^~~~
drivers/gpu/drm/sti/sti_hdmi.c:855:13: warning: this statement may fall through [-Wimplicit-fallthrough=]
   audio_cfg |= HDMI_AUD_CFG_CH34_VALID | HDMI_AUD_CFG_8CH;
drivers/gpu/drm/sti/sti_hdmi.c:856:2: note: here
  case 2:
  ^~~~

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/gpu/drm/sti/sti_hdmi.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/sti/sti_hdmi.c b/drivers/gpu/drm/sti/sti_hdmi.c
index f03d617edc4c..1617c5098a50 100644
--- a/drivers/gpu/drm/sti/sti_hdmi.c
+++ b/drivers/gpu/drm/sti/sti_hdmi.c
@@ -849,10 +849,13 @@ static int hdmi_audio_configure(struct sti_hdmi *hdmi)
 	switch (info->channels) {
 	case 8:
 		audio_cfg |= HDMI_AUD_CFG_CH78_VALID;
+		/* fall through */
 	case 6:
 		audio_cfg |= HDMI_AUD_CFG_CH56_VALID;
+		/* fall through */
 	case 4:
 		audio_cfg |= HDMI_AUD_CFG_CH34_VALID | HDMI_AUD_CFG_8CH;
+		/* fall through */
 	case 2:
 		audio_cfg |= HDMI_AUD_CFG_CH12_VALID;
 		break;
-- 
2.22.0