drm/amdgpu/gfx8: always restore kcq MQDs

Always restore the MQD not just when we do a reset.
This allows us to move the MQD to VRAM if we want.

v2: always reset ring pointer as well (Christian)

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>