drm/amdgpu/gfx9: fix driver reload with KIQ

Drop the KCQ disabling via KIQ.  We disable the MEC shortly
after anyway, so there is no need to wait for all of this.
Doing so seems to leave the MEC in a bad way.

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