habanalabs: use host va range for internal pools

Instead of using a dedicated va range for each internal pool,
we introduce a new way for reserving a va block from an existing
va range. This is a more generic way of reserving va blocks for
future use.

Signed-off-by: Ofir Bitton <obitton@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>