panfrost: Dynamically allocate array of texture pointers

panfrost: Dynamically allocate array of texture pointers

With 3D textures we can have lots of layers, so better allocate it
dynamically at runtime.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>