ipv4: don't spam dmesg with "Using LC-trie" messages

fib_trie_table() is called during netns creation and
Chromium uses clone(CLONE_NEWNET) to sandbox renderer process.

Don't print anything.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>