remove redundant dpdk source folder, this one is not maintained since last Nov.2016,

the other one is located in src/spdk/dpdk, which is alwasy maintained and used by spdk.
so remove this src/dpdk folder, we only need maintain one copy.

Signed-off-by: chunmei <chunmei.liu@intel.com>

diff --git a/src/dpdk b/src/dpdk
deleted file mode 160000 (submodule)
index d3bfeaa..0000000
--- a/src/dpdk
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit d3bfeaaabfd37ecc7d7d2edf2a3b60cc2d913cc9