examples/vhost_crypto: remove unused function

examples/vhost_crypto: remove unused function

This patch tries to fix the coverity issue of unchecked
return value. Since the function that causes the problem
is unused, it is removed completely.

Coverity issue: 336816
Fixes: f5188211c721 ("examples/vhost_crypto: add sample application")
Cc: stable@dpdk.org
Signed-off-by: Fan Zhang <roy.fan.zhang@intel.com>
Reviewed-by: Jens Freimann <jfreimann@redhat.com>
Acked-by: Marko Kovacevic <marko.kovacevic@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>