drm/amdgpu: add apu sequence in the imu v11

APU required to issue the enable GFX IMU message after IMU reset.

Signed-off-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Tim Huang <Tim.Huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>