Cargo: Update dependencies for the KVM serialization work

We need the project to rely on kvm-bindings and kvm-ioctls branches
which include the serde derive to be able to serialize and deserialize
some KVM structures.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

Cargo.toml

@@ -35,6 +35,7 @@ credibility = "0.1.3"
 tempdir= "0.3.7"
 lazy_static= "1.4.0"
 tempfile = "3.1.0"
+serde_json = ">=1.0.9"
 
 [features]
 default = ["acpi", "pci", "cmos"]