ipv4/fib_frontend: Allow RTM_F_CLONED flag to be used for filtering

This functionally reverts the check introduced by commit
e8ba330a ("rtnetlink: Update fib dumps for strict data checking")
as modified by commit e4e92fb1 ("net/ipv4: Bail early if user only
wants prefix entries").

As we are preparing to fix listing of IPv4 cached routes, we need to
give userspace a way to request them.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/fib_frontend.c

@@ -987,8 +987,8 @@ static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
 		filter.flags = rtm->rtm_flags & (RTM_F_PREFIX | RTM_F_CLONED);
 	}
 
-	/* fib entries are never clones and ipv4 does not use prefix flag */
-	if (filter.flags & (RTM_F_PREFIX | RTM_F_CLONED))
+	/* ipv4 does not use prefix flag */
+	if (filter.flags & RTM_F_PREFIX)
 		return skb->len;
 
 	if (filter.table_id) {