net:af_iucv: get rid of the unneeded variable 'err' in afiucv_pm_freeze

We will not use the variable 'err' after initalization, So remove it and
return 0.

Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>