drm/msm/mdp4: Remove empty prepare_commit() function

Remove empty prepare_commit() function from MDP4 driver.
Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Patchwork: https://patchwork.freedesktop.org/patch/523608/
Link: https://lore.kernel.org/r/20230221184256.1436-5-quic_jesszhan@quicinc.comSigned-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.c

@@ -84,10 +84,6 @@ static void mdp4_disable_commit(struct msm_kms *kms)
 	mdp4_disable(mdp4_kms);
 }
 
-static void mdp4_prepare_commit(struct msm_kms *kms, struct drm_atomic_state *state)
-{
-}
-
 static void mdp4_flush_commit(struct msm_kms *kms, unsigned crtc_mask)
 {
 	/* TODO */
@@ -154,7 +150,6 @@ static const struct mdp_kms_funcs kms_funcs = {
 		.disable_vblank  = mdp4_disable_vblank,
 		.enable_commit   = mdp4_enable_commit,
 		.disable_commit  = mdp4_disable_commit,
-		.prepare_commit  = mdp4_prepare_commit,
 		.flush_commit    = mdp4_flush_commit,
 		.wait_flush      = mdp4_wait_flush,
 		.complete_commit = mdp4_complete_commit,