net/iavf: simplify flow director rules for IP fragment

net/iavf: simplify flow director rules for IP fragment

This patch simplify the pattern of flow rules of FDIR for IP fragment.

Flow rule can be created by the following command:
1. flow create 0 ingress pattern eth /
   ipv4 fragment_offset spec 0x2000 fragment_offset mask 0x2000 /
   end <actions>
2. flow create 0 ingress pattern eth / ipv6 /
   ipv6_frag_ext fragment_offset spec 0x0001 fragment_offset mask 0x0001 /
   end <actions>

Signed-off-by: Wenjun Wu <wenjun1.wu@intel.com>
Acked-by: Qi Zhang <qi.z.zhang@intel.com>