accel/habanalabs: expose dram reserved size by kmd

We expose this in order for user applications to know how much dram
is reserved for internal use.

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