[PATCH][next] drm/amd/display: Fix fall-through warning for Clang

[Gustavo A. R. Silva]

In preparation to enable -Wimplicit-fallthrough for Clang, fix
the following warning by replacing a /* fall through */ comment
with the new pseudo-keyword macro fallthrough:

rivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_aux.c:672:4: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
                        case AUX_TRANSACTION_REPLY_I2C_OVER_AUX_DEFER:
                        ^

Notice that Clang doesn't recognize /* fall through */ comments as
implicit fall-through markings, so in order to globally enable
-Wimplicit-fallthrough for Clang, these comments need to be
replaced with fallthrough; in the whole codebase.

Link: https://github.com/KSPP/linux/issues/115
Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
---
JFYI: We had thousands of these sorts of warnings and now we are down
      to just 15 in linux-next. This is one of those last remaining
      warnings.

 drivers/gpu/drm/amd/display/dc/dce/dce_aux.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c b/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
index 28631714f697..2fb88e54a4bf 100644
--- a/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
+++ b/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
@@ -668,7 +668,7 @@ bool dce_aux_transfer_with_retries(struct ddc_service *ddc,
 				/* polling_timeout_period is in us */
 				defer_time_in_ms += aux110->polling_timeout_period / 1000;
 				++aux_defer_retries;
-				/* fall through */
+				fallthrough;
 			case AUX_TRANSACTION_REPLY_I2C_OVER_AUX_DEFER:
 				retry_on_defer = true;
 				fallthrough;
-- 
2.27.0