drm/amd/display: Fix memory leak

[why]
Resource release is needed on the error handling path
to prevent memory leak.

[how]
Fix this by adding kfree on the error handling path.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Yongzhi Liu <lyz_cs@pku.edu.cn>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>