drm/display: hdmi-cec-helper: Fix adapter unregistration

Attempting to reload a kernel module of an HDMI driver making use of the
new CEC helpers revealed a resource deallocation issue, i.e. the entries
in /dev/cec* keep growing.

Moreover, after a couple of tries the kernel crashes and the whole
system freezes:

[   47.515950] Unable to handle kernel paging request at virtual address 0020072007200778
[...]
[   47.521707] Internal error: Oops: 0000000096000004 [#1]  SMP
[...]
[   47.537597] Call trace:
[   47.537815]  klist_next+0x20/0x1b8 (P)
[   47.538152]  device_reorder_to_tail+0x74/0x120
[   47.538548]  device_reorder_to_tail+0x6c/0x120
[   47.538944]  device_pm_move_to_tail+0x78/0xd0
[   47.539334]  deferred_probe_work_func+0x9c/0x110
[   47.539747]  process_one_work+0x328/0x638
[   47.540108]  worker_thread+0x264/0x390
[   47.540445]  kthread+0x20c/0x230
[   47.540735]  ret_from_fork+0x10/0x20

Do a proper cleanup by calling cec_unregister_adapter() instead of
cec_delete_adapter() in the managed release action handler.

Fixes: 8b1a8f8 ("drm/display: add CEC helpers code")
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250703-hdmi-cec-helper-unreg-fix-v1-1-7e7b0eb578bb@collabora.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>

Author: cristicc

drivers/gpu/drm/display/drm_hdmi_cec_helper.c

@@ -69,7 +69,7 @@ static void drm_connector_hdmi_cec_adapter_unregister(struct drm_device *dev, vo
 	struct drm_connector *connector = res;
 	struct drm_connector_hdmi_cec_data *data = connector->cec.data;
 
-	cec_delete_adapter(data->adapter);
+	cec_unregister_adapter(data->adapter);
 
 	if (data->funcs->uninit)
 		data->funcs->uninit(connector);