drm/amdgpu/powerplay/psm: Fix memory leak in power state init

Commit 902bc65d ("drm/amdgpu/powerplay/psm: return an error in power
state init") made the power state init function return early in case of
failure to get an entry from the powerplay table, but it missed to clean up
the allocated memory for the current power state before returning.

Fixes: 902bc65d ("drm/amdgpu/powerplay/psm: return an error in power state init")
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Rafael Mendonca <rafaelmendsr@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>