drm/amdgpu/swsmu/vangogh: Only use RLCPowerNotify msg for disable

Per discussions with PMFW team, the driver only needs to
notify the PMFW when the RLC is disabled.  The RLC FW will notify
the PMFW directly when it's enabled.

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