drm/amdkfd: correct pipe offset calculation

Correct pipe offset calculation in is_pipe_enabled function,
it should be done in queues.

Signed-off-by: Jiansong Chen <Jiansong.Chen@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>