va: allocator: use _update_image_info() to set allocator parameters.

Use this standalone function to update the allocator info and make
all ensure_image() and mem_alloc() API clean.
We also change the default way of using image. We now set the non
derive manner as the default manner, and if it fails, then fallback
to the derived image manner.
On a lot of platforms, the derived image does not have caches, so the
read and write operations have very low performance.

Part-of: <!1698>