[FIB_TRIE]: Don't ignore negative results from fib_semantic_match

When a semantic match occurs either success, not found or an error
(for matching unreachable routes/blackholes) is returned. fib_trie
ignores the errors and looks for a different matching route. Treat
results other than "no match" as success and end lookup.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>