drm/amdgpu: Switch baremetal to use KIQ for compute ring management. (v3)

KIQ is the Kernel Interface Queue for managing the MEC.  Rather than setting
up rings via direct MMIO of ring registers, the rings are configured via
special packets sent to the KIQ.  The allows the MEC to better manage shared
resources and certain power events.

v2: squash in s3/s4 fix from Rex
v3: further fixes from Rex

Signed-off-by: David Panariti <David.Panariti@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Tom St Denis <tom.stdenis@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>