accel/habanalabs: add missing offset handling for dma-buf

On devices with virtual device memory (Gaudi2 onwards), user can provide
an offset within an allocated device memory from which he wants to
export a dma-buf object.
The offset value is verified by driver, but it is not taken into
consideration when the importer driver maps the dma-buf and the SG table
it prepared.
Add the missing offset handling.

Signed-off-by: Tomer Tayar <ttayar@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>