habanalabs: initialize hpriv fields before adding new node

When adding a new node to the hpriv list, the driver should
initialize its fields before adding the new node.

Otherwise, there may be some small chance of another thread traversing
that list and accessing the new node's fields without them being
initialized.

Signed-off-by: Moti Haimovski <mhaimovski@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>