Revert "drm/imx: Annotate dma-fence critical section in commit path"

This reverts commit f4b34faa.

Since commit f4b34faa ("drm/imx: Annotate dma-fence critical section in
commit path") the following possible circular dependency is detected:

[    5.001811] ======================================================
[    5.001817] WARNING: possible circular locking dependency detected
[    5.001824] 5.14.9-01225-g45da36cc6fcc-dirty #1 Tainted: G        W
[    5.001833] ------------------------------------------------------
[    5.001838] kworker/u8:0/7 is trying to acquire lock:
[    5.001848] c1752080 (regulator_list_mutex){+.+.}-{3:3}, at: regulator_lock_dependent+0x40/0x294
[    5.001903]
[    5.001903] but task is already holding lock:
[    5.001909] c176df78 (dma_fence_map){++++}-{0:0}, at: imx_drm_atomic_commit_tail+0x10/0x160
[    5.001957]
[    5.001957] which lock already depends on the new lock.
...

Revert it for now.

Tested on a imx6q-sabresd.

Fixes: f4b34faa ("drm/imx: Annotate dma-fence critical section in commit path")
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20211104001112.4035691-1-festevam@gmail.com

drivers/gpu/drm/imx/imx-drm-core.c

@@ -81,7 +81,6 @@ static void imx_drm_atomic_commit_tail(struct drm_atomic_state *state)
 	struct drm_plane_state *old_plane_state, *new_plane_state;
 	bool plane_disabling = false;
 	int i;
-	bool fence_cookie = dma_fence_begin_signalling();
 
 	drm_atomic_helper_commit_modeset_disables(dev, state);
 
@@ -112,7 +111,6 @@ static void imx_drm_atomic_commit_tail(struct drm_atomic_state *state)
 	}
 
 	drm_atomic_helper_commit_hw_done(state);
-	dma_fence_end_signalling(fence_cookie);
 }
 
 static const struct drm_mode_config_helper_funcs imx_drm_mode_config_helpers = {