tools/libx[cl]: Introduce struct xc_xend_cpuid for xc_cpuid_set()

tools/libx[cl]: Introduce struct xc_xend_cpuid for xc_cpuid_set()

In order to combine the functionality of xc_cpuid_set() with
xc_cpuid_apply_policy(), arrange to pass the data in a single contained
struct, rather than two arrays.

libxl__cpuid_policy is the ideal structure to use, but that would introduce a
reverse dependency between libxc and libxl.  Introduce xc_xend_cpuid (with a
transparent union to provide more useful names for the inputs), and use this
structure in libxl.

The public API has libxl_cpuid_policy as an opaque type referencing
libxl__cpuid_policy.  Drop the inappropriate comment about its internals, and
use xc_xend_cpuid as a differently named opaque backing object.  Users of both
libxl and libxc are not permitted to look at the internals.

No change in behaviour.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Release-acked-by: Paul Durrant <paul@xen.org>