Make sure to drop the reference to the dma device taken by
of_find_device_by_node() on probe errors and on driver unbind.
Fixes: 334ae614772b ("sparc: Kill SBUS DVMA layer.") Signed-off-by: Johan Hovold <johan@kernel.org> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>