dpdk: add support for v2.1.0

Update relevant artifacts to add support for DPDK v2.1.0
 - INSTALL.DPDK.md
 - acinclude.m4: Change DPDK library name
 - netdev-dpdk: Limit minimum mbuf size to to adapt to DPDK bug fix that
   changes the treatment of the requested mbuf size
 - build.sh: Change DPDK version number

Note that this breaks compatibility with DPDK v2.0.0 although only
for the library name change.

Note that throughput for vhost ports with mergeable buffers is reduced
about 10% due to a necessary bug fix in DPDK vhost code.

Signed-off-by: Mark Kavanagh <mark.b.kavanagh@intel.com>
Signed-off-by: Michal Weglicki <michalx.weglicki@intel.com>
Signed-off-by: Timo Puha <timox.puha@intel.com>
Acked-by: Daniele Di Proietto <diproiettod@vmware.com>

lib/netdev-dpdk.c

@@ -65,11 +65,17 @@ static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 20);
 /*
  * need to reserve tons of extra space in the mbufs so we can align the
  * DMA addresses to 4KB.
+ * The minimum mbuf size is limited to avoid scatter behaviour and drop in
+ * performance for standard Ethernet MTU.
  */
-
 #define MTU_TO_MAX_LEN(mtu)  ((mtu) + ETHER_HDR_LEN + ETHER_CRC_LEN)
-#define MBUF_SIZE(mtu)       (MTU_TO_MAX_LEN(mtu) + (512) + \
-                             sizeof(struct rte_mbuf) + RTE_PKTMBUF_HEADROOM)
+#define MBUF_SIZE_MTU(mtu)   (MTU_TO_MAX_LEN(mtu)        \
+                              + sizeof(struct dp_packet) \
+                              + RTE_PKTMBUF_HEADROOM)
+#define MBUF_SIZE_DRIVER     (2048                       \
+                              + sizeof (struct rte_mbuf) \
+                              + RTE_PKTMBUF_HEADROOM)
+#define MBUF_SIZE(mtu)       MAX(MBUF_SIZE_MTU(mtu), MBUF_SIZE_DRIVER)
 
 /* Max and min number of packets in the mempool.  OVS tries to allocate a
  * mempool with MAX_NB_MBUF: if this fails (because the system doesn't have