sched: cls_flower: remove from hashtable only in case skip sw flag is not set

Be symmetric to hashtable insert and remove filter from hashtable only
in case skip sw flag is not set.

Fixes: e69985c6 ("net/sched: cls_flower: Introduce support in SKIP SW flag")
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Amir Vadai <amir@vadai.me>
Signed-off-by: David S. Miller <davem@davemloft.net>