net: cdc_ncm: fix error path for single interface probing

commit bbc8d922 (net: cdc_ncm: add Huawei devices) implemented
support for devices with a single combined control and data
interface. Fix up the error path so that we do not double
release such interfaces in case of probing failures.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>