net/i40e: fix memory leak

net/i40e: fix memory leak

There are several func calls to rte_zmalloc() which don't have null
pointer check on the return value. And before return, the memory
is not freed. It fixes by adding null pointer check and rte_free().

Fixes: 078259773da9 ("net/i40e: store ethertype filter")
Fixes: 425c3325f0b0 ("net/i40e: store tunnel filter")
Fixes: c50474f31efe ("net/i40e: support tunnel filter to VF")
Fixes: 5c53c82c8174 ("net/i40e: store flow director filter")
Cc: stable@dpdk.org
Signed-off-by: Yong Wang <wang.yong19@zte.com.cn>
Acked-by: Beilei Xing <beilei.xing@intel.com>