s390/qeth: fix early exit from error path

[ Upstream commit 83cf79a2fec3cf499eb6cb9eb608656fc2a82776 ]

When the allocation of the addr buffer fails, we need to free
our refcount on the inetdevice before returning.

Signed-off-by: Julian Wiedmann <jwi@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>