i40e: Fix use-after-free in i40e_client_subtask()

stable inclusion
from stable-v4.19.191
commit c1322eaeb8af0d8985b5cc5fa759140fa0e57b84
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5RZPX


CVE: NA

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[ Upstream commit 38318f23a7ef86a8b1862e5e8078c4de121960c3 ]

Currently the call to i40e_client_del_instance frees the object
pf->cinst, however pf->cinst->lan_info is being accessed after
the free. Fix this by adding the missing return.

Addresses-Coverity: ("Read from pointer after free")
Fixes: 7b0b1a6d ("i40e: Disable iWARP VSI PETCP_ENA flag on netdev down events")
Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

Signed-off-by: tangbin <tangbin_yewu@cmss.chinamobile.com>