tc/f_flower: fix port range parsing

tc/f_flower: fix port range parsing

Provided port range in tc rule are parsed incorrectly.
Even though range is passed as min-max. It throws an error.

$ tc filter add dev eth0 ingress handle 100 priority 10000 protocol ipv4 flower ip_proto tcp dst_port 10368-61000 action pass
max value should be greater than min value
Illegal "dst_port"

Fixes: 8930840e678b ("tc: flower: Classify packets based port ranges")
Signed-off-by: Puneet Sharma <pusharma@akamai.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>