drm/amd/display: Decrement refcount of dc_sink before reassignment

stable inclusion
from stable-5.10.17
commit cd0604db18d22bc39dd8349d6b7ed2f8c79a627c
bugzilla: 48169

--------------------------------

[ Upstream commit 8e92bb0f ]

[why]
An old dc_sink state is causing a memory leak because it is missing a
dc_sink_release before a new dc_sink is assigned back to
aconnector->dc_sink.

[how]
Decrement the dc_sink refcount before reassigning it to a new dc_sink.

Signed-off-by: Victor Lu <victorchengchi.lu@amd.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>