We incorrectly compare the mask and the result is that we can't modify
an already existing rule.

Fix that by comparing correctly.

Fixes: 05cd271f ("cls_flower: Support multiple masks per priority")
Reported-by: Vlad Buslov <vladbu@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Paul Blakey <paulb@mellanox.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>