net: rtnl_dump_all needs to propagate error from dumpit function

If an address, route or netconf dump request is sent for AF_UNSPEC, then
rtnl_dump_all is used to do the dump across all address families. If one
of the dumpit functions fails (e.g., invalid attributes in the dump
request) then rtnl_dump_all needs to propagate that error so the user
gets an appropriate response instead of just getting no data.

Fixes: effe6792 ("net: Enable kernel side filtering of route dumps")
Fixes: 5fcd266a ("net/ipv4: Add support for dumping addresses for a specific device")
Fixes: 6371a71f ("net/ipv6: Add support for dumping addresses for a specific device")
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>