vhost/crypto: fix missing head correction

This patch fixes the missing head descriptor correction for
indirect descriptors.

Fixes: 0aee2428419f ("vhost/crypto: move to safe GPA translation API")

Signed-off-by: Fan Zhang <roy.fan.zhang@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

lib/librte_vhost/vhost_crypto.c

@@ -919,6 +919,7 @@ vhost_crypto_process_one_req(struct vhost_crypto *vcrypto,
 		if (unlikely(!desc || dlen != head->len))
 			return -1;
 		desc_idx = 0;
+		head = desc;
 	} else {
 		desc = head;
 	}