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: 8b1a8f8b2002 ("drm/display: add CEC helpers code")
Signed-off-by: Cristian Ciocaltea <[e-mail]>
Reviewed-by: Dmitry Baryshkov <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Baryshkov <[e-mail]>

drivers/gpu/drm/display/drm_hdmi_cec_helper.c

···
 	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);