drm/amdkfd: Rename create_cp_queue() to init_user_queue()

create_cp_queue() could also work with SDMA queues, so we should rename
it. It only initialize the data values rather than creating queues.

Signed-off-by: Yong Zhao <Yong.Zhao@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>