simplify msm_gpu_init(..)

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
do not try to create any ringbuffer for now

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
add basic impl of vivante_gpu_3d_init(..)

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>