drm/vc4: kms: Don't duplicate pending commit

Our HVS global state, when duplicated, will also copy the pointer to the
drm_crtc_commit (and increase the reference count) for each FIFO if the
pointer is not NULL.

However, our atomic_setup function will overwrite that pointer without
putting the reference back leading to a memory leak.

Since the commit is only relevant during the atomic commit process, it
doesn't make sense to duplicate the reference to the commit anyway.
Let's remove it.

Fixes: 9ec03d7f1e ("drm/vc4: kms: Wait on previous FIFO users before a commit")
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Tested-by: Jian-Hong Pan <jhp@endlessos.org>
Link: https://lore.kernel.org/r/20211117094527.146275-6-maxime@cerno.tech

drivers/gpu/drm/vc4/vc4_kms.c

@@ -676,12 +676,6 @@ vc4_hvs_channels_duplicate_state(struct drm_private_obj *obj)
 
 	for (i = 0; i < HVS_NUM_CHANNELS; i++) {
 		state->fifo_state[i].in_use = old_state->fifo_state[i].in_use;
-
-		if (!old_state->fifo_state[i].pending_commit)
-			continue;
-
-		state->fifo_state[i].pending_commit =
-			drm_crtc_commit_get(old_state->fifo_state[i].pending_commit);
 	}
 
 	return &state->base;