drm/amdkfd: Introduce asic-specific mqd_manager_init function

Global function mqd_manager_init just calls asic-specific functions and it
is not necessary. Delete it and introduce a mqd_manager_init interface in
dqm for asic-specific mqd manager init. Call mqd_manager_init interface
directly to initialize mqd manager

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>