habanalabs: modify export dmabuf API

A previous commit deprecated the option to export from handle, leaving
the code with no support for devices with virtual memory.

This commit modifies the export API in a way that unifies the uAPI to
user address for both cases (i.e. with and without MMU support) and add
the actual support for devices with virtual memory.

Signed-off-by: Ohad Sharabi <osharabi@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>