drm/amd/powerplay:clean up the residual mutex for smu_hw_init

The mutex for procting SMU during hw_init was removed as system
will be deadlock when smu_populate_umd_state_clk try get SMU mutex.
Therefore need remove the residual mutex from failed path.

Signed-off-by: Prike Liang <Prike.Liang@amd.com>
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>