Move kvm-ioctls crate to own directory

In preparation for creating a common workspace for kvm-bindings and
kvm-ioctls, move the kvm-ioctls crate to its own directory.

A workspace Cargo.toml is not added yet because it makes git detect it
as a modification and treat kvm-ioctls/Cargo.toml as a new file
instead of a rename.

Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>

Author: epilys