net_util: Move virtio-net helpers to net_util crate

Moving helpers to the net_util crate since we don't want virtio-net
common code to be split between two places. The net_util crate should be
the only place to host virtio-net common code.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

net_util/Cargo.toml

@@ -11,6 +11,8 @@ log = "0.4.14"
 net_gen = { path = "../net_gen" }
 rate_limiter = { path = "../rate_limiter" }
 serde = "1.0.126"
+versionize = "0.1.6"
+versionize_derive = "0.1.4"
 virtio-bindings = "0.1.0"
 vm-memory = { version = "0.5.0", features = ["backend-mmap", "backend-atomic"] }
 vm-virtio = { path = "../vm-virtio" }