Fixes the following sparse warnings:

net/ncsi/ncsi-manage.c:41:5: warning:
 symbol 'ncsi_get_filter' was not declared. Should it be static?
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>