drm/amdkfd: Init mqd managers in device queue manager init

Previously mqd managers was initialized on demand. As there
are only a few type of mqd managers, the on demand initialization
doesn't save too much memory. Initialize them on device
queue initialization instead and delete the get_mqd_manager
interface. This makes codes more organized for future changes.

Signed-off-by: Oak Zeng <ozeng@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>