examples/kni: print release error
examples/kni: print release error

In kni_free_kni: Value returned from a function is not checked for errors
before being used

Coverity issue: 30692
Fixes: b475eb0bc400 ("examples/kni: new parameters")

Signed-off-by: Daniel Mrzyglod <998f22cc3a6ac3535545292178d834b83a4e2a87@intel.com>
Acked-by: Helin Zhang <aba9dfdb1a6ec8bf1ff66b95272c029f8dfde1b1@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk