drm/ast: removed optional dummy encoder mode_fixup function.

mode_fixup function for encoder drivers became optional with patch
http://patchwork.freedesktop.org/patch/msgid/1455106522-32307-1-git-send-email-palminha@synopsys.com

This patch set nukes all the dummy mode_fixup implementations.

(made on top of Daniel topic/drm-misc branch)
Signed-off-by: Carlos Palminha <palminha@synopsys.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/12e1e900724c890166b88b0f4d67baba387482af.1455540137.git.palminha@synopsys.com

drivers/gpu/drm/ast/ast_mode.c

@@ -710,13 +710,6 @@ static void ast_encoder_dpms(struct drm_encoder *encoder, int mode)
 
 }
 
-static bool ast_mode_fixup(struct drm_encoder *encoder,
-			   const struct drm_display_mode *mode,
-			   struct drm_display_mode *adjusted_mode)
-{
-	return true;
-}
-
 static void ast_encoder_mode_set(struct drm_encoder *encoder,
 			       struct drm_display_mode *mode,
 			       struct drm_display_mode *adjusted_mode)
@@ -736,7 +729,6 @@ static void ast_encoder_commit(struct drm_encoder *encoder)
 
 static const struct drm_encoder_helper_funcs ast_enc_helper_funcs = {
 	.dpms = ast_encoder_dpms,
-	.mode_fixup = ast_mode_fixup,
 	.prepare = ast_encoder_prepare,
 	.commit = ast_encoder_commit,
 	.mode_set = ast_encoder_mode_set,