drm/amdgpu: refactor MQD/HQD initialization v3

The MQD programming sequence currently exists in 3 different places.
Refactor it to absorb all the duplicates.

The success path remains mostly identical except for a slightly
different order in the non-kiq case. This shouldn't matter if the HQD
is disabled.

The error handling paths have been updated to deal with the new code
structure.

v2: the non-kiq path for gfxv8 was dropped in the rebase
v3: split MEC_HPD_SIZE rename, dropped doorbell changes

Reviewed-by: Edward O'Callaghan <funfunctor@folklore1984.net>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Andres Rodriguez <andresx7@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>