remove useless line in dpdk cryptodev

Change-Id: I2ef33c7c15b3eb1f55bbfd5cbdd230d6a4d58936
Signed-off-by: Simon Zhang <yuwei1.zhang@intel.com>
diff --git a/src/plugins/dpdk/ipsec/esp_encrypt.c b/src/plugins/dpdk/ipsec/esp_encrypt.c
index 2a8d610..cdeeb40 100644
--- a/src/plugins/dpdk/ipsec/esp_encrypt.c
+++ b/src/plugins/dpdk/ipsec/esp_encrypt.c
@@ -470,8 +470,6 @@
 		}
 	    }
 
-	  vnet_buffer (b0)->sw_if_index[VLIB_RX] =
-	    vnet_buffer (b0)->sw_if_index[VLIB_RX];
 	  b0->flags |= VLIB_BUFFER_TOTAL_LENGTH_VALID;
 
 	  /* mbuf packet starts at ESP header */