net: Set fput_needed iff FDPUT_FPUT is set

We should fput() file iff FDPUT_FPUT is set. So we should set fput_needed
accordingly.

Fixes: 00e188ef ("sockfd_lookup_light(): switch to fdget^W^Waway from fget_light")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>