drm/amd/display: Fix memory leak in dcn21_clock_source_create

[ Upstream commit 65e54987508b6f0771f56bdfa3ee1926d52785ae ]

When dcn20_clk_src_construct() fails, we need to release clk_src.

Fixes: 6f4e6361 ("drm/amd/display: Add Renoir resource (v2)")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>