drm/amdkfd: Cleanup DQM ASIC-specific ops

Remove empty initialize function.

Rename register_process to update_qpd to avoid confusion with the
non-ASIC-specific register_process.

Shorten ops_asic_specific to asic_ops.

Signed-off-by: Yong Zhao <yong.zhao@amd.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>