sfc: Make failed filter removal less noisy

There are situations - mostly reset related - where our view of the
filter table differs from the hardware. In this case we may try and
remove filters that aren't actually installed. This isn't that
interesting in most situations, so downgrade the logging.

Signed-off-by: Bert Kenward <bkenward@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>