netdev_unregister_timeout_secs=0 can lead to printing the
"waiting for dev to become free" message every jiffy.
This is too frequent and unnecessary.
Set the min value to 1 second.

Also fix the merge issue introduced by
"net: make unregister netdev warning timeout configurable":
it changed "refcnt != 1" to "refcnt".
Signed-off-by: NDmitry Vyukov <dvyukov@google.com>
Suggested-by: NEric Dumazet <edumazet@google.com>
Fixes: 5aa3afe1 ("net: make unregister netdev warning timeout configurable")
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>