Update Makefile for reserving FF_DPDK for x86

The former patch, which add compiler option for arm64, removes the FF_DPDK for x86.
That's a mistake.

Author: dgbo

lib/Makefile

@@ -24,18 +24,18 @@ FF_KNI=1
 #FF_IPFW=1
 
 ifeq ($(FF_DPDK),)
-ifeq (${MACHINE_CPUARCH},aarch64)
+ifeq (${shell uname -m},aarch64)
     FF_DPDK=${TOPDIR}/dpdk/build
 else
-    #FF_DPDK=${TOPDIR}/dpdk/x86_64-native-linuxapp-gcc
+    FF_DPDK=${TOPDIR}/dpdk/x86_64-native-linuxapp-gcc
 endif
 endif
 
 ifdef RTE_SDK
-ifeq (${MACHINE_CPUARCH},aarch64) 
+ifeq (${shell uname -m},aarch64) 
     FF_DPDK=${RTE_SDK}/build
 else
-    #FF_DPDK=${RTE_SDK}/x86_64-native-linuxapp-gcc
+    FF_DPDK=${RTE_SDK}/x86_64-native-linuxapp-gcc
 endif
 endif