drm/amd/pm: Fix a memory leak on an error path

Add missing free on an error path.

Fixes: 511a9555

 ("drm/amd/pm: Add SMU 13.0.6 support")
Reviewed-by: Yang Wang <kevinyang.wang@amd.com>
Signed-off-by: Kunwu.Chan <chentao@kylinos.cn>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>