argo: introduce the argo_op hypercall boilerplate

argo: introduce the argo_op hypercall boilerplate

Presence is gated upon CONFIG_ARGO.

Registers the hypercall previously reserved for this.
Takes 5 arguments, does nothing and returns -ENOSYS.

Implementation will provide a compat ABI so COMPAT_CALL is the selected
macro for the hypercall tables.

Signed-off-by: Christopher Clark <christopher.clark6@baesystems.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Juergen Gross <jgross@suse.com>